A203768 a(n)=f(a(n-1),a(n-2),a(n-3)+1), where f(x,y,z)=yz+zx+xy and (a(1),a(2),a(3))=(0,0,1).

0, 0, 1, 1, 3, 11, 61, 959, 70739, 72283977, 5182756776363, 374996904946945687251, 1943544856497336440989864767424605, 728823315884977144637506322934226372105715052561182439

Offset: 1

Author

Clark Kimberling, Jan 07 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A203761.

Crossrefs

Cf. A203761, A203769.

Programs

Mathematica

a[1] = 0; a[2] = 0; a[3] = 1;
a[n_] := SymmetricPolynomial[2, {a[n - 1], a[n - 2], 1 + a[n - 3]}]
Table[a[n], {n, 1, 16}]  (* A203768 *)
(Rest[Rest[%]] - 1)/2    (* A203769 *)