A319214 a(n) = phi(n^5 - 1)/5 where phi is A000010.

6, 22, 120, 280, 1240, 1120, 5400, 5280, 12960, 12880, 45240, 24752, 90240, 59160, 96000, 141984, 346880, 163800, 540000, 326720, 588984, 585120, 1523280, 582400, 1728000, 1203840, 2294712, 1758096, 4692408, 1388000, 6480000, 3787200, 5416800, 4783680, 7440000

Offset

2,1

Links

Seiichi Manyama, Table of n, a(n) for n = 2..1000

Eric Weisstein's World of Mathematics, Totient Function.

Wikipedia, Euler's totient function.

Formula

Sum_{k=1..n} a(k) = c * n^6 + O((n*log(n))^5), where c = (1/30) * Product_{p prime == 1 (mod 5)} (1 - 5/p^2) * Product_{p prime !== 1 (mod 5)} (1 - 1/p^2) = 0.019389107739... . - Amiram Eldar, Dec 09 2024

Mathematica

Table[EulerPhi[n^5-1]/5, {n, 2, 40}] (* Harvey P. Dale, Feb 09 2019 *)

Prog

(PARI) {a(n) = eulerphi(n^5-1)/5}

Crossrefs

Row 5 of A369291.

Cf. A000010, A258807 (n^5-1).

phi(n^b - 1)/b: A319210 (b=2), A319213 (b=3), this sequence (b=5).

Sequence in context: A179601 A151495 A193463 * A009358 A213130 A002137

Adjacent sequences: A319211 A319212 A319213 * A319215 A319216 A319217

Keyword

nonn,easy

Author

Seiichi Manyama, Sep 13 2018

Status

approved