OFFSET
0,3
LINKS
Paul D. Hanna, Table of n, a(n) for n = 0..100
PROG
(PARI) {ITERATE(F, n, k) = my(G=x +x*O(x^k)); for(i=1, n, G=subst(G, x, F)); G}
{A274391(n, k) = my(TREE = serreverse(x*exp(-x +x*O(x^k)))); k!*polcoeff(exp(ITERATE(TREE, n, k)), k)}
/* Print table A274391 */
for(n=0, 10, for(k=0, 10, print1(A274391(n, k), ", ")); print("..."))
/* Print this sequence as the main diagonal in A274391 */
for(n=0, 20, print1(A274391(n, n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jun 24 2016
STATUS
approved