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Theorem phisum 15333
 Description: The divisor sum identity of the totient function. Theorem 2.2 in [ApostolNT] p. 26. (Contributed by Stefan O'Rear, 12-Sep-2015.)
Assertion
Ref Expression
phisum (𝑁 ∈ ℕ → Σ𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (ϕ‘𝑑) = 𝑁)
Distinct variable group:   𝑥,𝑁,𝑑

Proof of Theorem phisum
Dummy variables 𝑧 𝑦 𝑤 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 breq1 4586 . . . . . 6 (𝑥 = 𝑦 → (𝑥𝑁𝑦𝑁))
21elrab 3331 . . . . 5 (𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↔ (𝑦 ∈ ℕ ∧ 𝑦𝑁))
3 hashgcdeq 15332 . . . . . . 7 ((𝑁 ∈ ℕ ∧ 𝑦 ∈ ℕ) → (#‘{𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = if(𝑦𝑁, (ϕ‘(𝑁 / 𝑦)), 0))
43adantrr 749 . . . . . 6 ((𝑁 ∈ ℕ ∧ (𝑦 ∈ ℕ ∧ 𝑦𝑁)) → (#‘{𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = if(𝑦𝑁, (ϕ‘(𝑁 / 𝑦)), 0))
5 iftrue 4042 . . . . . . 7 (𝑦𝑁 → if(𝑦𝑁, (ϕ‘(𝑁 / 𝑦)), 0) = (ϕ‘(𝑁 / 𝑦)))
65ad2antll 761 . . . . . 6 ((𝑁 ∈ ℕ ∧ (𝑦 ∈ ℕ ∧ 𝑦𝑁)) → if(𝑦𝑁, (ϕ‘(𝑁 / 𝑦)), 0) = (ϕ‘(𝑁 / 𝑦)))
74, 6eqtrd 2644 . . . . 5 ((𝑁 ∈ ℕ ∧ (𝑦 ∈ ℕ ∧ 𝑦𝑁)) → (#‘{𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = (ϕ‘(𝑁 / 𝑦)))
82, 7sylan2b 491 . . . 4 ((𝑁 ∈ ℕ ∧ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}) → (#‘{𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = (ϕ‘(𝑁 / 𝑦)))
98sumeq2dv 14281 . . 3 (𝑁 ∈ ℕ → Σ𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (#‘{𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = Σ𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (ϕ‘(𝑁 / 𝑦)))
10 fzfi 12633 . . . . 5 (1...𝑁) ∈ Fin
11 dvdsssfz1 14878 . . . . 5 (𝑁 ∈ ℕ → {𝑥 ∈ ℕ ∣ 𝑥𝑁} ⊆ (1...𝑁))
12 ssfi 8065 . . . . 5 (((1...𝑁) ∈ Fin ∧ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ⊆ (1...𝑁)) → {𝑥 ∈ ℕ ∣ 𝑥𝑁} ∈ Fin)
1310, 11, 12sylancr 694 . . . 4 (𝑁 ∈ ℕ → {𝑥 ∈ ℕ ∣ 𝑥𝑁} ∈ Fin)
14 fzofi 12635 . . . . . 6 (0..^𝑁) ∈ Fin
15 ssrab2 3650 . . . . . 6 {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} ⊆ (0..^𝑁)
16 ssfi 8065 . . . . . 6 (((0..^𝑁) ∈ Fin ∧ {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} ⊆ (0..^𝑁)) → {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} ∈ Fin)
1714, 15, 16mp2an 704 . . . . 5 {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} ∈ Fin
1817a1i 11 . . . 4 ((𝑁 ∈ ℕ ∧ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}) → {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} ∈ Fin)
19 oveq1 6556 . . . . . . . . . 10 (𝑧 = 𝑤 → (𝑧 gcd 𝑁) = (𝑤 gcd 𝑁))
2019eqeq1d 2612 . . . . . . . . 9 (𝑧 = 𝑤 → ((𝑧 gcd 𝑁) = 𝑦 ↔ (𝑤 gcd 𝑁) = 𝑦))
2120elrab 3331 . . . . . . . 8 (𝑤 ∈ {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} ↔ (𝑤 ∈ (0..^𝑁) ∧ (𝑤 gcd 𝑁) = 𝑦))
2221simprbi 479 . . . . . . 7 (𝑤 ∈ {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} → (𝑤 gcd 𝑁) = 𝑦)
2322rgen 2906 . . . . . 6 𝑤 ∈ {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} (𝑤 gcd 𝑁) = 𝑦
2423rgenw 2908 . . . . 5 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}∀𝑤 ∈ {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} (𝑤 gcd 𝑁) = 𝑦
25 invdisj 4571 . . . . 5 (∀𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}∀𝑤 ∈ {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} (𝑤 gcd 𝑁) = 𝑦Disj 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦})
2624, 25mp1i 13 . . . 4 (𝑁 ∈ ℕ → Disj 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦})
2713, 18, 26hashiun 14395 . . 3 (𝑁 ∈ ℕ → (#‘ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = Σ𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (#‘{𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}))
28 fveq2 6103 . . . 4 (𝑑 = (𝑁 / 𝑦) → (ϕ‘𝑑) = (ϕ‘(𝑁 / 𝑦)))
29 eqid 2610 . . . . 5 {𝑥 ∈ ℕ ∣ 𝑥𝑁} = {𝑥 ∈ ℕ ∣ 𝑥𝑁}
30 eqid 2610 . . . . 5 (𝑧 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↦ (𝑁 / 𝑧)) = (𝑧 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↦ (𝑁 / 𝑧))
3129, 30dvdsflip 14877 . . . 4 (𝑁 ∈ ℕ → (𝑧 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↦ (𝑁 / 𝑧)):{𝑥 ∈ ℕ ∣ 𝑥𝑁}–1-1-onto→{𝑥 ∈ ℕ ∣ 𝑥𝑁})
32 oveq2 6557 . . . . . 6 (𝑧 = 𝑦 → (𝑁 / 𝑧) = (𝑁 / 𝑦))
33 ovex 6577 . . . . . 6 (𝑁 / 𝑦) ∈ V
3432, 30, 33fvmpt 6191 . . . . 5 (𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} → ((𝑧 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↦ (𝑁 / 𝑧))‘𝑦) = (𝑁 / 𝑦))
3534adantl 481 . . . 4 ((𝑁 ∈ ℕ ∧ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}) → ((𝑧 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↦ (𝑁 / 𝑧))‘𝑦) = (𝑁 / 𝑦))
36 elrabi 3328 . . . . . . 7 (𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} → 𝑑 ∈ ℕ)
3736adantl 481 . . . . . 6 ((𝑁 ∈ ℕ ∧ 𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}) → 𝑑 ∈ ℕ)
3837phicld 15315 . . . . 5 ((𝑁 ∈ ℕ ∧ 𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}) → (ϕ‘𝑑) ∈ ℕ)
3938nncnd 10913 . . . 4 ((𝑁 ∈ ℕ ∧ 𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}) → (ϕ‘𝑑) ∈ ℂ)
4028, 13, 31, 35, 39fsumf1o 14301 . . 3 (𝑁 ∈ ℕ → Σ𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (ϕ‘𝑑) = Σ𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (ϕ‘(𝑁 / 𝑦)))
419, 27, 403eqtr4rd 2655 . 2 (𝑁 ∈ ℕ → Σ𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (ϕ‘𝑑) = (#‘ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}))
42 elfzoelz 12339 . . . . . . . . . . 11 (𝑧 ∈ (0..^𝑁) → 𝑧 ∈ ℤ)
4342adantl 481 . . . . . . . . . 10 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → 𝑧 ∈ ℤ)
44 nnz 11276 . . . . . . . . . . 11 (𝑁 ∈ ℕ → 𝑁 ∈ ℤ)
4544adantr 480 . . . . . . . . . 10 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → 𝑁 ∈ ℤ)
46 nnne0 10930 . . . . . . . . . . . . 13 (𝑁 ∈ ℕ → 𝑁 ≠ 0)
4746neneqd 2787 . . . . . . . . . . . 12 (𝑁 ∈ ℕ → ¬ 𝑁 = 0)
4847intnand 953 . . . . . . . . . . 11 (𝑁 ∈ ℕ → ¬ (𝑧 = 0 ∧ 𝑁 = 0))
4948adantr 480 . . . . . . . . . 10 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → ¬ (𝑧 = 0 ∧ 𝑁 = 0))
50 gcdn0cl 15062 . . . . . . . . . 10 (((𝑧 ∈ ℤ ∧ 𝑁 ∈ ℤ) ∧ ¬ (𝑧 = 0 ∧ 𝑁 = 0)) → (𝑧 gcd 𝑁) ∈ ℕ)
5143, 45, 49, 50syl21anc 1317 . . . . . . . . 9 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → (𝑧 gcd 𝑁) ∈ ℕ)
52 gcddvds 15063 . . . . . . . . . . 11 ((𝑧 ∈ ℤ ∧ 𝑁 ∈ ℤ) → ((𝑧 gcd 𝑁) ∥ 𝑧 ∧ (𝑧 gcd 𝑁) ∥ 𝑁))
5343, 45, 52syl2anc 691 . . . . . . . . . 10 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → ((𝑧 gcd 𝑁) ∥ 𝑧 ∧ (𝑧 gcd 𝑁) ∥ 𝑁))
5453simprd 478 . . . . . . . . 9 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → (𝑧 gcd 𝑁) ∥ 𝑁)
55 breq1 4586 . . . . . . . . . 10 (𝑥 = (𝑧 gcd 𝑁) → (𝑥𝑁 ↔ (𝑧 gcd 𝑁) ∥ 𝑁))
5655elrab 3331 . . . . . . . . 9 ((𝑧 gcd 𝑁) ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↔ ((𝑧 gcd 𝑁) ∈ ℕ ∧ (𝑧 gcd 𝑁) ∥ 𝑁))
5751, 54, 56sylanbrc 695 . . . . . . . 8 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → (𝑧 gcd 𝑁) ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁})
58 risset 3044 . . . . . . . . 9 ((𝑧 gcd 𝑁) ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↔ ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}𝑦 = (𝑧 gcd 𝑁))
59 eqcom 2617 . . . . . . . . . 10 (𝑦 = (𝑧 gcd 𝑁) ↔ (𝑧 gcd 𝑁) = 𝑦)
6059rexbii 3023 . . . . . . . . 9 (∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁}𝑦 = (𝑧 gcd 𝑁) ↔ ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦)
6158, 60bitri 263 . . . . . . . 8 ((𝑧 gcd 𝑁) ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} ↔ ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦)
6257, 61sylib 207 . . . . . . 7 ((𝑁 ∈ ℕ ∧ 𝑧 ∈ (0..^𝑁)) → ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦)
6362ralrimiva 2949 . . . . . 6 (𝑁 ∈ ℕ → ∀𝑧 ∈ (0..^𝑁)∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦)
64 rabid2 3096 . . . . . 6 ((0..^𝑁) = {𝑧 ∈ (0..^𝑁) ∣ ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦} ↔ ∀𝑧 ∈ (0..^𝑁)∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦)
6563, 64sylibr 223 . . . . 5 (𝑁 ∈ ℕ → (0..^𝑁) = {𝑧 ∈ (0..^𝑁) ∣ ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦})
66 iunrab 4503 . . . . 5 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} = {𝑧 ∈ (0..^𝑁) ∣ ∃𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (𝑧 gcd 𝑁) = 𝑦}
6765, 66syl6reqr 2663 . . . 4 (𝑁 ∈ ℕ → 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦} = (0..^𝑁))
6867fveq2d 6107 . . 3 (𝑁 ∈ ℕ → (#‘ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = (#‘(0..^𝑁)))
69 nnnn0 11176 . . . 4 (𝑁 ∈ ℕ → 𝑁 ∈ ℕ0)
70 hashfzo0 13077 . . . 4 (𝑁 ∈ ℕ0 → (#‘(0..^𝑁)) = 𝑁)
7169, 70syl 17 . . 3 (𝑁 ∈ ℕ → (#‘(0..^𝑁)) = 𝑁)
7268, 71eqtrd 2644 . 2 (𝑁 ∈ ℕ → (#‘ 𝑦 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} {𝑧 ∈ (0..^𝑁) ∣ (𝑧 gcd 𝑁) = 𝑦}) = 𝑁)
7341, 72eqtrd 2644 1 (𝑁 ∈ ℕ → Σ𝑑 ∈ {𝑥 ∈ ℕ ∣ 𝑥𝑁} (ϕ‘𝑑) = 𝑁)
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 383   = wceq 1475   ∈ wcel 1977  ∀wral 2896  ∃wrex 2897  {crab 2900   ⊆ wss 3540  ifcif 4036  ∪ ciun 4455  Disj wdisj 4553   class class class wbr 4583   ↦ cmpt 4643  ‘cfv 5804  (class class class)co 6549  Fincfn 7841  0cc0 9815  1c1 9816   / cdiv 10563  ℕcn 10897  ℕ0cn0 11169  ℤcz 11254  ...cfz 12197  ..^cfzo 12334  #chash 12979  Σcsu 14264   ∥ cdvds 14821   gcd cgcd 15054  ϕcphi 15307 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-8 1979  ax-9 1986  ax-10 2006  ax-11 2021  ax-12 2034  ax-13 2234  ax-ext 2590  ax-rep 4699  ax-sep 4709  ax-nul 4717  ax-pow 4769  ax-pr 4833  ax-un 6847  ax-inf2 8421  ax-cnex 9871  ax-resscn 9872  ax-1cn 9873  ax-icn 9874  ax-addcl 9875  ax-addrcl 9876  ax-mulcl 9877  ax-mulrcl 9878  ax-mulcom 9879  ax-addass 9880  ax-mulass 9881  ax-distr 9882  ax-i2m1 9883  ax-1ne0 9884  ax-1rid 9885  ax-rnegex 9886  ax-rrecex 9887  ax-cnre 9888  ax-pre-lttri 9889  ax-pre-lttrn 9890  ax-pre-ltadd 9891  ax-pre-mulgt0 9892  ax-pre-sup 9893 This theorem depends on definitions:  df-bi 196  df-or 384  df-an 385  df-3or 1032  df-3an 1033  df-tru 1478  df-fal 1481  df-ex 1696  df-nf 1701  df-sb 1868  df-eu 2462  df-mo 2463  df-clab 2597  df-cleq 2603  df-clel 2606  df-nfc 2740  df-ne 2782  df-nel 2783  df-ral 2901  df-rex 2902  df-reu 2903  df-rmo 2904  df-rab 2905  df-v 3175  df-sbc 3403  df-csb 3500  df-dif 3543  df-un 3545  df-in 3547  df-ss 3554  df-pss 3556  df-nul 3875  df-if 4037  df-pw 4110  df-sn 4126  df-pr 4128  df-tp 4130  df-op 4132  df-uni 4373  df-int 4411  df-iun 4457  df-disj 4554  df-br 4584  df-opab 4644  df-mpt 4645  df-tr 4681  df-eprel 4949  df-id 4953  df-po 4959  df-so 4960  df-fr 4997  df-se 4998  df-we 4999  df-xp 5044  df-rel 5045  df-cnv 5046  df-co 5047  df-dm 5048  df-rn 5049  df-res 5050  df-ima 5051  df-pred 5597  df-ord 5643  df-on 5644  df-lim 5645  df-suc 5646  df-iota 5768  df-fun 5806  df-fn 5807  df-f 5808  df-f1 5809  df-fo 5810  df-f1o 5811  df-fv 5812  df-isom 5813  df-riota 6511  df-ov 6552  df-oprab 6553  df-mpt2 6554  df-om 6958  df-1st 7059  df-2nd 7060  df-wrecs 7294  df-recs 7355  df-rdg 7393  df-1o 7447  df-oadd 7451  df-er 7629  df-en 7842  df-dom 7843  df-sdom 7844  df-fin 7845  df-sup 8231  df-inf 8232  df-oi 8298  df-card 8648  df-pnf 9955  df-mnf 9956  df-xr 9957  df-ltxr 9958  df-le 9959  df-sub 10147  df-neg 10148  df-div 10564  df-nn 10898  df-2 10956  df-3 10957  df-n0 11170  df-xnn0 11241  df-z 11255  df-uz 11564  df-rp 11709  df-fz 12198  df-fzo 12335  df-fl 12455  df-mod 12531  df-seq 12664  df-exp 12723  df-hash 12980  df-cj 13687  df-re 13688  df-im 13689  df-sqrt 13823  df-abs 13824  df-clim 14067  df-sum 14265  df-dvds 14822  df-gcd 15055  df-phi 15309 This theorem is referenced by: (None)
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