A320851 Number of 5-element subsets of [n] whose sum is a triangular number.

1, 1, 4, 9, 18, 35, 61, 100, 156, 235, 342, 482, 664, 895, 1185, 1542, 1977, 2505, 3134, 3879, 4757, 5782, 6968, 8337, 9909, 11699, 13732, 16030, 18615, 21514, 24755, 28361, 32362, 36789, 41673, 47051, 52953, 59412, 66466, 74158, 82525, 91611, 101454, 112097

Offset: 5

Author

Alois P. Heinz, Oct 22 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 5..1000

Crossrefs

Column k=5 of A284249.

Cf. A000217.