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A115882 Numbers n such that n plus the n-th prime gives a triangular number. 6
1, 20, 49, 65, 103, 176, 279, 284, 299, 437, 513, 553, 656, 973, 1271, 1779, 1921, 2156, 2312, 2347, 2554, 2759, 3176, 3379, 4008, 4028, 4132, 5255, 6354, 6764, 7116, 8299, 8334, 8366, 8723, 9277, 9755, 10092, 10475, 10631, 11429, 11842, 12633, 13157, 13627 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

EXAMPLE

103+prime(103)=103+563=666=T(36).

MATHEMATICA

TriangularQ[n_] := IntegerQ[Sqrt[1 + 8*n]]; Select[Range[20000], TriangularQ[# + Prime[#]] &] (* T. D. Noe, Jan 27 2014 *)

PROG

(PARI) isok(n) = ispolygonal(n + prime(n), 3); \\ Michel Marcus, Jan 25 2014

CROSSREFS

Cf. A064371, A115883, A115886.

Sequence in context: A177725 A264444 A053245 * A277553 A260093 A007589

Adjacent sequences:  A115879 A115880 A115881 * A115883 A115884 A115885

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 06 2006

STATUS

approved

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Last modified June 27 11:25 EDT 2017. Contains 288788 sequences.