OFFSET
0,2
REFERENCES
R. A. Rankin, Modular Forms, p. 240 ff.
E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, NY, 1985, p. 121.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..5000
FORMULA
G.f.: 1 + 8*Sum_{k>0} k^5 x^k/(1+(-x)^k). - Michael Somos, Sep 21 2005
MATHEMATICA
a[0] = 1; a[n_] := (-1)^(n-1)*8*DivisorSum[n, (-1)^(n + n/#)*#^5&]; Table[a[n], {n, 0, 26}] (* Jean-François Alcover, Jul 06 2017, translated from PARI *)
PROG
(PARI) a(n)=if(n<1, n==0, (-1)^(n-1)*8*sumdiv(n, d, (-1)^(n+n/d)*d^5)) /* Michael Somos, Sep 21 2005 */
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved