OFFSET
0,5
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..105
FORMULA
a(n)=n!*sum(j=0..n/3, binomial(n-3*j,j)/(n-3*j)!)
Recurrence: a(n) = a(n-1) + 4*(n-3)*(n-2)*(n-1)*a(n-4). - Vaclav Kotesovec, Jun 26 2013
a(n) ~ 2^(n/2-1)*exp(n^(1/4)/sqrt(2)-3*n/4)*n^(3*n/4). - Vaclav Kotesovec, Jun 26 2013
MATHEMATICA
CoefficientList[Series[E^(x+x^4), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Jun 26 2013 *)
PROG
(Maxima)
a(n):=n!*sum(binomial(n-3*j, j)/(n-3*j)!, j, 0, n/3);
(PARI) Vec(serlaplace(exp(x+x^4+O(x^66)))) /* Joerg Arndt, May 24 2011 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, May 22 2011
STATUS
approved