OFFSET
1,4
COMMENTS
For a guide to related sequences, see A203761.
MATHEMATICA
a[1] = 0; a[2] = 0; a[3] = 1;
a[n_] := SymmetricPolynomial[2, {1 + a[n - 1], 1 + a[n - 2], a[n - 3]}]
Table[a[n], {n, 1, 16}] (* A203901 *)
nxt[{a_, b_, c_}]:={b, c, Total[Times@@@Subsets[{a, b+1, c+1}, {2}]]}; NestList[nxt, {0, 0, 1}, 15][[All, 1]] (* Harvey P. Dale, Nov 01 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jan 07 2012
STATUS
approved