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A118565 Numbers which are both lucky and triangular. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

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 *)

CROSSREFS

Cf. A000959, A000217.

Sequence in context: A171570 A076825 A259745 * A230658 A117801 A347303

Adjacent sequences:  A118562 A118563 A118564 * A118566 A118567 A118568

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

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

STATUS

approved

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Last modified October 21 02:29 EDT 2021. Contains 348141 sequences. (Running on oeis4.)