A259693 a(n) = Sum(k^5*sigma(k)*sigma(n-k),k=1..n-1).

0, 1, 99, 1264, 10475, 44820, 185626, 546560, 1454841, 3640950, 7868245, 16042176, 31040789, 59796968, 97525350, 177090560, 276689076, 467100189, 681356055, 1096023200, 1533162960, 2426544252, 3205401854, 4885539840, 6250705625, 9431254430, 11831779350

Offset

1,3

Comments

This was formerly A001478.

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(5);

Prog

(PARI) a(n) = sum(k=1, n-1, k^5*sigma(k)*sigma(n-k)) \\ Colin Barker, Jul 16 2015

Crossrefs

Cf. A000385, A000441, A000477, A000499, A259692, A259694, A259695, A259696.

Sequence in context: A338258 A201044 A196577 * A196785 A196808 A305721

Adjacent sequences: A259690 A259691 A259692 * A259694 A259695 A259696

Keyword

nonn

Author

N. J. A. Sloane, Jul 03 2015

Status

approved