A374193 a(n) is the smallest number which can be represented as the sum of two nonzero pentagonal pyramidal numbers in exactly n ways, or -1 if no such number exists.

2, 1471, 269406

Offset: 1

Author

Ilya Gutkovskiy, Jun 30 2024

Keywords

• nonn
• hard
• more
• bref

Comments

There are no further positive terms <= 10^15. - Michael S. Branicky, Jul 01 2024

Examples

			a(2) = 1471 = 1 + 1470 = 288 + 1183.
		

Links

• Eric Weisstein's World of Mathematics, Pentagonal Pyramidal Number

Crossrefs

Cf. A002411, A011541, A332989, A334013, A374168, A374194.