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Search: id:A122513
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| A122513 |
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Numbers n such that 1+2n+3n^2 is a triangular number. |
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+0
1
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| 0, 1, 46, 135, 4540, 13261, 444906, 1299475, 43596280
(list; graph; listen)
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OFFSET
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1,3
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EXAMPLE
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Corresponding values of triangular numbers tri=m(m+1)/2 and m's are
tri = 1, 6, 6441, 54946, 61843881, 527588886, 593824936321
m = 1, 3, 113, 331, 11121, 32483, 1089793
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MATHEMATICA
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triQ[n_] := IntegerQ[ Sqrt[8n + 1]]; lst = {}; Do[ If[ triQ[1 + 2n + 3n^2], AppendTo[lst, n]; Print@n], {n, 0, 65000000}] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A000217 = triangular numbers, A086285 = numbers n such that 1+2n+3n^2 is prime.
Sequence in context: A044297 A044678 A074866 this_sequence A053019 A044378 A044759
Adjacent sequences: A122510 A122511 A122512 this_sequence A122514 A122515 A122516
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Oct 20 2006
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EXTENSIONS
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a(8) & a(9) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 08 2007
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