A319183 a(n) = phi(n^n - 1)/n where phi is A000010.

1, 4, 32, 280, 5040, 37856, 829440, 15676416, 589032000, 10374307328, 388566097920, 7619466454080, 390751784579520, 11138729990400000, 575561351791902720, 24328359845627701248, 1640651748984970444800, 34709116765970413844280, 2459108342476800000000000

Offset

2,2

Comments

Main diagonal of the array T(n,k) = phi(n^k-1)/k for n > 1 and k > 1, which starts

1, 2, 2, 6, 6, 18, 16, ... A011260

2, 4, 8, 22, 48, 156, 320, ... A027385

4, 12, 32, 120, 288, 1512, 4096, ... A027695

4, 20, 48, 280, 720, 5580, 14976, ... A027741

12, 56, 216, 1240, 5040, 31992, 139968, ... A295496

8, 36, 160, 1120, 6048, 37856, 192000, ... A027743

18, 144, 432, 5400, 23328, 254016, 829440, ... A027744

Links

Seiichi Manyama, Table of n, a(n) for n = 2..50

Eric Weisstein's World of Mathematics, Totient Function.

Wikipedia, Euler's totient function.

Mathematica

Table[EulerPhi[n^n-1]/n, {n, 20}] (* Harvey P. Dale, Aug 04 2020 *)

Prog

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

Crossrefs

A diagonal of A369291.

Cf. A000010, A006486, A027385.

Sequence in context: A246818 A145710 A264633 * A199566 A370160 A366663

Adjacent sequences: A319180 A319181 A319182 * A319184 A319185 A319186

Keyword

nonn

Author

Seiichi Manyama, Sep 12 2018

Status

approved