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
Keywords
Links
- Eric Weisstein's World of Mathematics, Totient Function.
Programs
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Mathematica
nmax = 50; Accumulate[Table[EulerPhi[j], {j, 1, nmax}]]^2 (* Vaclav Kotesovec, May 08 2024 *) -
PARI
a(n) = sum(j=1, n, sum(k=1, n, eulerphi(j)*eulerphi(k)));
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PARI
a(n) = sum(k=1, n, eulerphi(k))^2;
Formula
a(n) = A002088(n)^2.
a(n) ~ 9*n^4/(Pi^4). - Vaclav Kotesovec, May 08 2024