OFFSET
0,2
LINKS
Paul D. Hanna and Charles R Greathouse IV, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: [x^(n^2)] G(x)^3 where G(x) = Sum_{k>=0} x^(k^2); the notation [x^(n^2)] G(x)^3 denotes the coefficient of x^(n^2) in G(x)^3. [From Paul D. Hanna, Apr 20 2012]
MATHEMATICA
nn=100; t=Table[0, {nn}]; Do[n=Sqrt[a^2+b^2+c^2]; If[n<=nn && IntegerQ[n], t[[n]]++], {a, 0, nn}, {b, 0, nn}, {c, 0, nn}]; Prepend[t, 1]
PROG
(PARI) {a(n)=local(G=sum(k=0, n, x^(k^2)+x*O(x^(n^2)))); polcoeff(G^3, n^2)} /* Paul D. Hanna */
(PARI) A(n)=my(G=sum(k=0, n, x^(k^2), x*O(x^(n^2)))^3); vector(n+1, k, polcoeff(G, (k-1)^2)) \\ Charles R Greathouse IV, Apr 20 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Nov 12 2010
STATUS
approved