A203772 - OEIS

%I #5 Mar 30 2012 18:58:07

%S 0,0,1,3,11,74,1232,108084,141466347,15464951390151,

%T 2189441739723579832963,33859919808724254529558716855414396,

%U 74134322256556148244446056491575979484293791968668948464

%N a(n)=f(a(n-1),a(n-2)+1,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], 1 + a[n - 2], 1 + a[n - 3]}]

%t Table[a[n], {n, 1, 14}]  (* A203772 *)

%Y Cf. A203761.

%K nonn

%O 1,4

%A _Clark Kimberling_, Jan 07 2012