A374273 a(n) is the smallest number which can be represented as the sum of three distinct nonzero n-gonal numbers in exactly n ways, or -1 if no such number exists.

37, 161, 498, 1666, 2546, 7434, 16609, 25952, 48786, 49861, 72347, 127335, 183289, 196469, 416913, 466546, 494369, 506649, 801010, 1401011, 2372586, 1414009, 2003027, 3274986, 2927260, 2721677, 5592756, 8016592, 6632759, 7057914, 8401837, 13248146, 11648679, 8650006

Offset: 3

Author

Ilya Gutkovskiy, Jul 02 2024

Keywords

• nonn

Examples

			a(3) = 37 = 1 + 15 + 21 = 3 + 6 + 28 = 6 + 10 + 21.
a(4) = 161 = 1^2 + 4^2 + 12^2 = 2^2 + 6^2 + 11^2 = 4^2 + 8^2 + 9^2 = 5^2 + 6^2 + 10^2.
		

Links

• Eric Weisstein's World of Mathematics, Polygonal Number

Crossrefs

Cf. A025415, A057145, A350405, A374144, A374274.

Extensions

a(21) and beyond from Michael S. Branicky, Jul 08 2024