OFFSET
0,4
PROG
(PARI) {a(n)= local(A); if(n<3, n>=0, A=vector(n, i, 1); for(k=1, n-2, A[k+2]=(k-1)*A[k+1]+ k*A[k]+ 2); A[n])} /* Michael Somos, Nov 19 2006 */
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved