A203768 - OEIS

%I #6 Mar 30 2012 18:58:07

%S 0,0,1,1,3,11,61,959,70739,72283977,5182756776363,

%T 374996904946945687251,1943544856497336440989864767424605,

%U 728823315884977144637506322934226372105715052561182439

%N 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).

%C For a guide to related sequences, see A203761.

%t a[1] = 0; a[2] = 0; a[3] = 1;

%t a[n_] := SymmetricPolynomial[2, {a[n - 1], a[n - 2], 1 + a[n - 3]}]

%t Table[a[n], {n, 1, 16}]  (* A203768 *)

%t (Rest[Rest[%]] - 1)/2    (* A203769 *)

%Y Cf. A203761, A203769.

%K nonn

%O 1,5

%A _Clark Kimberling_, Jan 07 2012