A363253 a(n) is the smallest n-gonal number which can be represented as the sum of distinct nonzero n-gonal numbers in exactly n ways, or -1 if no such number exists.

28, 121, 210

Offset: 3

Author

Ilya Gutkovskiy, May 23 2023

Keywords

• nonn
• bref
• more
• hard

Comments

a(8) = 736, a(9) = 969.

Examples

			For n = 3: 1 + 6 + 21 = 3 + 10 + 15 = 28.
		

Links

• Eric Weisstein's World of Mathematics, Polygonal Number

Crossrefs

Cf. A057145, A350207, A350405, A350423.