OFFSET
4,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 4..577
Wikipedia, Partition of a set
MATHEMATICA
b[n_, m_, t_] := b[n, m, t] = If[n == 0, {1, 0}, Sum[If[t == 1 && j != m + 1, 0, Function[p, p + If[j == -t || t == 1 && j == m + 1, {0, p[[1]]}, 0]][b[n - 1, Max[m, j], If[t == 1 && j == m + 1, -j, If[t < 0, t, If[t > 0, t - 1, 0]]]]]], {j, 1, m + 1}]];
a[n_] := b[n, 0, Max[0, 1 + n - 4]][[2]];
Array[a, 24, 4] (* Jean-François Alcover, May 26 2018, from Maple code for A270701 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 22 2016
STATUS
approved