A234141 Numbers k such that triangular(k) - m is a triangular number (A000217), where m is the largest square less than triangular(k).

1, 4, 5, 7, 10, 13, 16, 19, 21, 22, 25, 28, 40, 42, 59, 60, 64, 76, 85, 89, 93, 109, 110, 124, 127, 142, 144, 148, 161, 165, 178, 184, 195, 212, 229, 233, 246, 247, 263, 265, 268, 280, 297, 313, 314, 331, 346, 348, 349, 365, 373, 376, 382, 399, 416, 433, 445, 450

Offset

1,2

Comments

The sequence of triangular(a(n)) begins: 1, 10, 15, 28, 55, 91, 136, 190, 231, 253, 325, ...

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[450], IntegerQ@Sqrt[8 ((#^2 + #)/2 - (Ceiling@Sqrt[(#^2 + #)/2] - 1)^2) + 1] &] (* Ivan Neretin, May 29 2016 *)

Crossrefs

Cf. A000217, A000290, A234142, A234143.

Sequence in context: A187479 A013947 A202342 * A093517 A248858 A145018

Adjacent sequences: A234138 A234139 A234140 * A234142 A234143 A234144

Keyword

nonn

Author

Alex Ratushnyak, Dec 19 2013

Status

approved