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 A188893 The index of the least triangular number greater than 1 that is also an n-gonal number, or 0 if none exists. 2
 2, 8, 20, 3, 10, 6, 25, 4, 0, 14, 8, 50, 5, 9, 21, 0, 43, 23, 6, 154, 11, 16, 26, 56, 12, 7, 49, 34, 40, 342, 19, 25, 1634, 8, 115, 0, 33, 89, 15, 47, 54, 638, 9, 36, 117, 30, 99, 204, 38, 17, 146, 133, 10, 62, 70, 18, 41, 49, 34, 4806, 105, 161, 329, 11, 439, 223, 28, 5974, 20, 79 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS MATHEMATICA NgonIndex[n_, v_] := (-4 + n + Sqrt[16 - 8*n + n^2 - 16*v + 8*n*v])/(n - 2)/2; Table[k = 2; While[tr = k*(k+1)/2; i = NgonIndex[n, tr]; k < 20000 && ! IntegerQ[i], k++]; If[k==20000, k=0]; k, {n, 3, 50}] CROSSREFS Cf. A188891. Sequence in context: A240285 A129445 A082821 * A227127 A227399 A327098 Adjacent sequences:  A188890 A188891 A188892 * A188894 A188895 A188896 KEYWORD nonn AUTHOR T. D. Noe, Apr 13 2011 STATUS approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)