%I
%S 1,7,5859,3201146676,3820181459144204700,
%T 25381616622722369500521817413900,
%U 2012800150183968180465350145758736863679028900800,3623820214658807704726540455788270697258988626189027049678195383091200
%N Vandermonde sequence using x^2  xy + y^2 applied to the first n triangular numbers: 1,3,6,10,...,n(n+1)/2.
%C See A093883 for a discussion and guide to related sequences.
%t f[j_] := j (j + 1)/2; z = 11;
%t u[n_] := Product[f[j]^2  f[j] f[k] + f[k]^2,
%t {j, 1, k  1}]
%t v[n_] := Product[u[n], {k, 2, n}]
%t Table[v[n], {n, 1, z}] (* A203693 *)
%t Table[v[n + 1]/v[n], {n, 1, z}] (* A203694 *)
%K nonn
%O 1,2
%A _Clark Kimberling_, Jan 04 2012
