A259694 a(n) = Sum(k^6*sigma(k)*sigma(n-k),k=1..n-1).

0, 1, 195, 3496, 38195, 192780, 977386, 3216320, 9860049, 27321870, 65803045, 144005856, 308944925, 635774072, 1112550390, 2153146880, 3618341556, 6391671525, 9949570455, 16725562160, 24691972080, 40979569092, 56807498030, 89450231040, 120404165825

Offset

1,3

Comments

This was formerly A001479.

Links

Colin Barker, Table of n, a(n) for n = 1..1000

J. Touchard, On prime numbers and perfect numbers, Scripta Math., 129 (1953), 35-39. [Annotated scanned copy]

Maple

S:=(n, e)->add(k^e*sigma(k)*sigma(n-k), k=1..n-1); f:=e->[seq(S(n, e), n=1..30)]; f(6);

Prog

(PARI) a(n) = sum(k=1, n-1, k^6*sigma(k)*sigma(n-k)) \\ Colin Barker, Jul 16 2015

Crossrefs

Cf. A000385, A000441, A000477, A000499, A259692, A259693, A259695, A259696.

Sequence in context: A172354 A295130 A257765 * A066232 A284960 A226105

Adjacent sequences: A259691 A259692 A259693 * A259695 A259696 A259697

Keyword

nonn

Author

N. J. A. Sloane, Jul 03 2015

Status

approved