OFFSET
5,2
FORMULA
Euler transform of period 9 sequence [ -12, -12, -12, -12, -12, -12, -12, -12, -24, ...]. - Michael Somos, Sep 21 2005
G.f.: x^5 * (Product_{k>0} (1 - x^k) * (1 - x^(9*k)))^12. - Michael Somos, Sep 21 2005
EXAMPLE
G.f. = q^5 - 12*q^6 + 54*q^7 - 88*q^8 - 99*q^9 + 540*q^10 - 418*q^11 + ...
MATHEMATICA
a[ n_] := SeriesCoefficient[ q^5 (QPochhammer[ q] QPochhammer[ q^9])^12, {q, 0, n}]; (* Michael Somos, Feb 22 2015 *)
PROG
(PARI) {a(n) = local(A); if( n<5, 0, n-=5; A = x *O(x^n); polcoeff( (eta(x + A) * eta(x^9 + A))^12, n))}; /* Michael Somos, Sep 21 2005 */
CROSSREFS
KEYWORD
sign
AUTHOR
STATUS
approved