A332985 - OEIS

A332985

Index of triangular numbers that are sum of two pentagonal numbers (A332984).

3, 4, 8, 14, 32, 34, 41, 42, 46, 47, 49, 53, 58, 63, 66, 67, 69, 71, 76, 79, 82, 86, 89, 90, 100, 101, 102, 110, 113, 117, 124, 129, 141, 151, 159, 168, 175, 178, 183, 186, 192, 195, 205, 216, 217, 219, 232, 241, 247, 250, 252, 253, 255, 258, 261, 263, 265, 271, 284, 293, 297, 298

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

The index of a triangular number T is the integer n such that T = n*(n+1)/2.

LINKS

Peter Kagey, Table of n, a(n) for n = 1..1000

CROSSREFS

Cf. A000217 (triangular numbers), A000326 (pentagonal numbers), A332987 (sums of two nonzero pentagonal numbers).

Sequence in context: A049866 A118355 A026632 * A026654 A104370 A310013

Adjacent sequences: A332982 A332983 A332984 * A332986 A332987 A332988

KEYWORD

nonn,easy

AUTHOR

Olivier Gérard, Mar 05 2020

STATUS

approved