OFFSET
0,4
FORMULA
a(n) = n! * Sum_{k=0..floor(n/3)} (2*n-4*k)! * |Stirling1(n-2*k,k)|/( (n-2*k)! * (2*n-5*k+1)! ).
PROG
(PARI) a(n) = n!*sum(k=0, n\3, (2*n-4*k)!*abs(stirling(n-2*k, k, 1))/((n-2*k)!*(2*n-5*k+1)!));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 15 2024
STATUS
approved