A115882 Numbers k such that k + prime(k) gives a triangular number.

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

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 * A303295 A277553 A260093

Adjacent sequences: A115879 A115880 A115881 * A115883 A115884 A115885

Keyword

nonn

Author

Giovanni Resta, Feb 06 2006

Status

approved