OFFSET
0,1
FORMULA
Expansion of q^(-2/3) * (a(q) * c(q))^2 in powers of q where a(), c() are cubic AGM theta functions. - Michael Somos, May 30 2012
Convolution square of A144614. - Michael Somos, May 30 2012
Sum_{k=0..n} a(k) ~ (20*zeta(4)/3) * n^4. - Amiram Eldar, Dec 12 2023
EXAMPLE
G.f. = 9 + 126*x + 585*x^2 + 1332*x^3 + 3096*x^4 + 4914*x^5 + 9198*x^6 + 12168*x^7 + ...
G.f. = 9*q^2 + 126*q^5 + 585*q^8 + 1332*q^11 + 3096*q^14 + 4914*q^17 + 9198*q^20 + ...
MATHEMATICA
Table[DivisorSigma[3, 3n+2], {n, 0, 40}] (* Harvey P. Dale, Jul 02 2011 *)
PROG
(PARI) {a(n) = if( n<0, 0, sigma( 3*n + 2, 3))}; /* Michael Somos, May 30 2012 */
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Mar 20 2004
STATUS
approved