A074763 - OEIS

A074763

a(n) = (1/n) * Sum_{d divides n} (-1)^(n+d)*phi(n/d)*2^d.

2, 1, 4, 4, 8, 10, 20, 34, 60, 100, 188, 348, 632, 1162, 2192, 4114, 7712, 14542, 27596, 52480, 99880, 190558, 364724, 699248, 1342184, 2580796, 4971068, 9587560, 18512792, 35790376, 69273668, 134219794, 260301176, 505286416, 981706832

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OFFSET

1,1

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 1..3000

FORMULA

G.f.: Sum_{k>=1} phi(k)*log(1/(1 + 2*(-x)^k))/k. - Ilya Gutkovskiy, May 23 2019

a(n) ~ 2^n / n. - Vaclav Kotesovec, Jul 23 2026

MATHEMATICA

Table[1/n*Sum[(-1)^(n+d)*EulerPhi[n/d]*2^d, {d, Divisors[n]}], {n, 1, 50}] (* Vaclav Kotesovec, Jul 23 2026 *)

CROSSREFS

Cf. A000010, A000031, A038063.

Sequence in context: A300622 A394291 A195691 * A099932 A175000 A355020

Adjacent sequences: A074760 A074761 A074762 * A074764 A074765 A074766

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Sep 06 2002

STATUS

approved