A356485 a(n) = n! * Sum_{k=1..n} A000010(k)/k.

1, 3, 13, 64, 416, 2736, 23472, 207936, 2113344, 22584960, 284722560, 3576337920, 52240412160, 768727895040, 12228344755200, 206114911027200, 3838718125670400, 71231050830643200, 1468632692485324800, 30345814652977152000, 666456931810639872000, 15172961921551171584000

Offset

1,2

Links

Table of n, a(n) for n=1..22.

Eric Weisstein's World of Mathematics, Totient Function.

Formula

a(n) ~ n! * 6*n/Pi^2.

Mathematica

Table[n! * Sum[EulerPhi[k]/k, {k, 1, n}], {n, 1, 25}]

Prog

(PARI) a(n) = n!*sum(k=1, n, eulerphi(k)/k); \\ Michel Marcus, Aug 09 2022

Crossrefs

Cf. A000010, A002088, A011755, A356297, A356010, A356298, A356323.

Sequence in context: A020086 A151987 A369796 * A126149 A060927 A074537

Adjacent sequences: A356482 A356483 A356484 * A356486 A356487 A356488

Keyword

nonn

Author

Vaclav Kotesovec, Aug 09 2022

Status

approved