OFFSET
2,2
MATHEMATICA
A[m_, n_]:=Sum[Sum[Binomial[n, d]StirlingS2[n-d, i](m^(m-1)-1)^(n-d-i), {d, 0, n-i}], {i, 0, n}]; a[n_]=Sum[A[n-m+1, m], {m, 0, n-2}]; Array[a, 15, 2]
CROSSREFS
KEYWORD
nonn
AUTHOR
Stefano Spezia, Jul 04 2023
STATUS
approved