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 A203691 Vandermonde sequence using x^2 + xy + y^2 applied to the first n triangular numbers: 1,3,6,10,...,n(n+1)/2. 3
 1, 13, 35217, 106499166228, 1193900625351298928700, 125977443935710401573828500229372900, 267622663746762354024098339277838006317831656007585600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS See A093883 for a discussion and guide to related sequences. LINKS MATHEMATICA f[j_] := j (j + 1)/2; z = 11; u[n_] := Product[f[j]^2 + f[j] f[k] + f[k]^2, {j, 1, k - 1}] v[n_] := Product[u[n], {k, 2, n}] Table[v[n], {n, 1, z}] (* A203691 *) Table[v[n + 1]/v[n], {n, 1, z}] (* A203692 *) CROSSREFS Sequence in context: A124990 A013752 A076811 * A220981 A258670 A048917 Adjacent sequences: A203688 A203689 A203690 * A203692 A203693 A203694 KEYWORD nonn AUTHOR Clark Kimberling, Jan 04 2012 STATUS approved

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Last modified November 29 18:13 EST 2022. Contains 358431 sequences. (Running on oeis4.)