A379376 Number of sets of nonzero n-gonal numbers whose largest element is the n-th n-gonal number and whose sum is an n-gonal number.
2, 2, 2, 1, 2, 4, 6, 4, 7, 10, 23, 32, 49, 87, 140, 257, 480, 803, 1311, 2450
Offset: 3
Examples
a(8) = 4 sets: {176}, {8, 96, 176}, {1, 8, 40, 176} and {8, 21, 40, 96, 176}.
a(9) = 6 sets: {261}, {9, 204, 261}, {24, 111, 261}, {75, 111, 204, 261}, {9, 24, 111, 154, 261} and {1, 9, 46, 75, 154, 204, 261}.
Links
- Eric Weisstein's World of Mathematics, Polygonal Number