OFFSET
1,2
LINKS
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
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 08 2024
STATUS
approved