OFFSET
1,1
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..45
FORMULA
a(n) = (3^n - 1)^n.
E.g.f.: Sum_{n>=0} 3^(n^2) * exp(-3^n*x) * x^n/n!. - Paul D. Hanna, Dec 26 2011
O.g.f.: Sum_{n>=0} 3^(n^2) * x^n/(1+3^n*x)^(n+1). - Paul D. Hanna, Dec 26 2011
PROG
(PARI) a(n)={(3^n - 1)^n} \\ Harry J. Smith, Jul 08 2009
(PARI) {a(n, q=3, m=1, b=-1)=(m*q^n + b)^n} \\ Paul D. Hanna, Dec 26 2011
(PARI) /* E.g.f. series identity: */
{a(n, q=3, m=1, b=-1)=n!*polcoeff(sum(k=0, n, m^k*q^(k^2)*exp(b*q^k*x+x*O(x^n))*x^k/k!), n)} \\ Paul D. Hanna, Dec 26 2011
(PARI) /* O.g.f. series identity: */
{a(n, q=3, m=1, b=-1)=polcoeff(sum(k=0, n, m^k*q^(k^2)*x^k/(1-b*q^k*x+x*O(x^n))^(k+1)), n)} \\ Paul D. Hanna, Dec 26 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 25 2001
EXTENSIONS
More terms from Harry J. Smith, Jul 08 2009
STATUS
approved