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A370321
Expansion of e.g.f. (1 + x + x^2)^(x^2).
0
1, 0, 0, 6, 12, -80, 540, 3528, -35280, 82080, 3346560, -33153120, -82257120, 6269253120, -54446648256, -587596363200, 20753512416000, -140977071406080, -3956109141496320, 111209937855367680, -474928112845670400, -36237656611756615680, 911155391189543808000
OFFSET
0,4
FORMULA
a(n) = n! * Sum_{j=0..n} Sum_{k=0..floor(j/2)} binomial(j-k,n-j-k) * Stirling1(j-k,k)/(j-k)!.
PROG
(PARI) a(n) = n!*sum(j=0, n, sum(k=0, j\2, binomial(j-k, n-j-k)*stirling(j-k, k, 1)/(j-k)!));
CROSSREFS
Cf. A371157.
Sequence in context: A061520 A305058 A220232 * A196253 A338563 A345271
KEYWORD
sign
AUTHOR
Seiichi Manyama, Mar 14 2024
STATUS
approved