OFFSET
3,4
COMMENTS
Also number of standard Young tableaux with last row of length 3.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 3..100
MATHEMATICA
b[n_, l_List] := b[n, l] = If[n < 1, x^l[[-1]], b[n - 1, Append[l, 1]] + Sum[If[i == 1 || l[[i - 1]] > l[[i]], b[n - 1, ReplacePart[l, i -> l[[i]] + 1]], 0], {i, 1, Length[l]}]]; a[n_] := Coefficient[b[n - 1, {1}], x, 3]; Table[a[n], {n, 3, 30}] (* Jean-François Alcover, Feb 10 2015, after A238123 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Joerg Arndt and Alois P. Heinz, Jun 20 2014
STATUS
approved