A372635 a(n) = Sum_{j=1..n} Sum_{k=1..n} phi(j)*phi(k).

1, 4, 16, 36, 100, 144, 324, 484, 784, 1024, 1764, 2116, 3364, 4096, 5184, 6400, 9216, 10404, 14400, 16384, 19600, 22500, 29584, 32400, 40000, 44944, 52900, 58564, 72900, 77284, 94864, 104976, 118336, 129600, 147456, 156816, 186624, 202500, 224676, 240100, 280900

Offset

1,2

Links

Table of n, a(n) for n=1..41.

Eric Weisstein's World of Mathematics, Totient Function.

Formula

a(n) = A002088(n)^2.

a(n) ~ 9*n^4/(Pi^4). - Vaclav Kotesovec, May 08 2024

Mathematica

nmax = 50; Accumulate[Table[EulerPhi[j], {j, 1, nmax}]]^2 (* Vaclav Kotesovec, May 08 2024 *)

Prog

(PARI) a(n) = sum(j=1, n, sum(k=1, n, eulerphi(j)*eulerphi(k)));
(PARI) a(n) = sum(k=1, n, eulerphi(k))^2;

Crossrefs

Cf. A000010, A002088, A372633.

Sequence in context: A207436 A189145 A005722 * A075408 A206981 A318149

Adjacent sequences: A372632 A372633 A372634 * A372636 A372637 A372638

Keyword

nonn

Author

Seiichi Manyama, May 08 2024

Status

approved