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A320855
Number of 9-element subsets of [n] whose sum is a triangular number.
2
1, 1, 6, 21, 64, 174, 419, 930, 1921, 3741, 6933, 12303, 21044, 34839, 56044, 87885, 134682, 202181, 297873, 431423, 615166, 864673, 1199421, 1643537, 2226716, 2985188, 3962845, 5212562, 6797615, 8793297, 11288719, 14388852, 18216738, 22915930, 28653268
OFFSET
9,3
LINKS
CROSSREFS
Column k=9 of A284249.
Cf. A000217.
Sequence in context: A321947 A291226 A228704 * A319613 A117962 A105457
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 22 2018
STATUS
approved