A319210 - OEIS

A319210

a(n) = phi(n^2 - 1)/2 where phi is A000010.

1, 2, 4, 4, 12, 8, 18, 16, 30, 16, 60, 24, 48, 48, 64, 48, 144, 48, 108, 80, 132, 80, 220, 96, 180, 144, 252, 96, 420, 128, 300, 256, 240, 192, 432, 216, 432, 288, 480, 192, 840, 240, 504, 440, 552, 352, 966, 320, 672, 480, 832, 432, 1040, 432, 720, 672, 1044, 448

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,2

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.

MATHEMATICA

Table[(EulerPhi@(n^2 - 1) / 2), {n, 2, 70}] (* Vincenzo Librandi, Sep 15 2018 *)

PROG

(PARI) {a(n) = eulerphi(n^2-1)/2}

(Magma) [EulerPhi(n^2-1)/2: n in [2..70]]; // Vincenzo Librandi, Sep 15 2018