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

Author

Seiichi Manyama, Sep 12 2018

Keywords

• nonn

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.

Crossrefs

A diagonal of A369291.

Cf. A000010, A006486, A027385.

Programs

Mathematica

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

PARI

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