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

Offset: 1

Author

Olivier Gérard, Mar 05 2020

Keywords

• nonn
• easy

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).