A344526 a(n) = Sum_{k=1..n} k^3 * phi(k).

1, 9, 63, 191, 691, 1123, 3181, 5229, 9603, 13603, 26913, 33825, 60189, 76653, 103653, 136421, 215029, 250021, 373483, 437483, 548615, 655095, 922769, 1033361, 1345861, 1556773, 1911067, 2174491, 2857383, 3073383, 3967113, 4491401, 5210141, 5839005, 6868005, 7427877, 9251385

Offset: 1

Author

Seiichi Manyama, May 22 2021

Keywords

• nonn

Crossrefs

Cf. A000010, A011755, A068970, A319087, A344522.

Programs

Mathematica

a[n_] := Sum[k^3 * EulerPhi[k], {k, 1, n}]; Array[a, 40] (* Amiram Eldar, May 22 2021 *)
Accumulate[Table[k^3*EulerPhi[k], {k, 1, 40}]] (* Vaclav Kotesovec, May 22 2021 *)

PARI

a(n) = sum(k=1, n, k^3*eulerphi(k));

Formula

a(n) ~ 6*n^5 / (5*Pi^2). - Vaclav Kotesovec, May 22 2021