A054612 - OEIS

A054612

a(n) = Sum_{d|n} phi(d)*5^(n/d).

0, 5, 30, 135, 660, 3145, 15810, 78155, 391320, 1953405, 9768870, 48828175, 244157820, 1220703185, 6103593930, 30517584915, 152588282640, 762939453205, 3814699250430, 19073486328215, 95367441415140, 476837158360185, 2384185839844050

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OFFSET

0,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..1430

FORMULA

a(n) = Sum_{k=1..n} 5^gcd(n,k). - Ilya Gutkovskiy, Apr 16 2021

PROG

(PARI) a(n) = if (n, sumdiv(n, d, eulerphi(d)*5^(n/d)), 0); \\ Michel Marcus, Apr 16 2021

CROSSREFS

Column k=5 of A185651.

Cf. A001869.

Sequence in context: A196452 A227267 A213260 * A358543 A282078 A080951

Adjacent sequences: A054609 A054610 A054611 * A054613 A054614 A054615

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Apr 16 2000

STATUS

approved