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

1,1

Comments

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

Links

Table of n, a(n) for n=1..3.

Eric Weisstein's World of Mathematics, Pentagonal Pyramidal Number

Example

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

Crossrefs

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

Sequence in context: A170993 A259323 A172939 * A172234 A339543 A023291

Adjacent sequences: A374190 A374191 A374192 * A374194 A374195 A374196

Keyword

nonn,hard,more,bref

Author

Ilya Gutkovskiy, Jun 30 2024

Status

approved