A118565 Numbers which are both lucky and triangular.

1, 3, 15, 21, 105, 171, 231, 741, 903, 1275, 1485, 1711, 2211, 2415, 3003, 3403, 3655, 4095, 4465, 4851, 5151, 5253, 5671, 7503, 8001, 8515, 10153, 10585, 10731, 11781, 13203, 13695, 13861, 17391, 18145, 18915, 19503, 21115, 22155, 22791, 24531

Offset: 1

Author

Luc Stevens (lms022(AT)yahoo.com), May 07 2006

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..3537

Crossrefs

Cf. A000959, A000217.

Programs

Mathematica

triQ[n_] := IntegerQ@Sqrt[8n+1]; lst = Range[1, 26564, 2]; i = 2; While[ i <= (len = Length@lst) && (k = lst[[i]]) <= len, lst = Drop[lst, {k, len, k}]; i++ ]; Select[lst, triQ@# &] (* Robert G. Wilson v *)

Extensions

Corrected and extended by Adam Panagos (adam.panagos(AT)gmail.com) and Robert G. Wilson v, May 10 2006