OFFSET
1,3
COMMENTS
This was formerly A001480.
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(7);
MATHEMATICA
Table[Sum[k^7 DivisorSigma[1, k]DivisorSigma[1, n-k], {k, n-1}], {n, 30}] (* Harvey P. Dale, Dec 14 2015 *)
PROG
(PARI) a(n) = sum(k=1, n-1, k^7*sigma(k)*sigma(n-k)) \\ Colin Barker, Jul 16 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 03 2015
STATUS
approved