A284251 Number of n-element subsets of [2n] whose sum is a triangular number.

1, 1, 2, 5, 11, 35, 106, 337, 1112, 3741, 12821, 44576, 156862, 557580, 1999117, 7221134, 26253632, 95996850, 352798772, 1302457652, 4828002125, 17962539164, 67052864821, 251066424023, 942692613615, 3548654963966, 13390078255129, 50635057984917

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..100

Formula

a(n) = A284249(2n,n).

Crossrefs

Cf. A281872, A284249.

Sequence in context: A196690 A101834 A117758 * A343162 A353210 A295495

Adjacent sequences: A284248 A284249 A284250 * A284252 A284253 A284254

Keyword

nonn

Author

Alois P. Heinz, Mar 23 2017

Status

approved