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
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 0..100
Formula
a(n) = A284249(2n,n).