A374143 a(n) is the smallest number which can be represented as the sum of two distinct nonzero octagonal numbers in exactly n ways, or -1 if no such number exists.

9, 1053, 12641, 68141, 365641, 953181, 2830641, 6232341, 13969041, 23211261, 104733741, 84994021, 175873641, 159851141, 538547641, 602713041, 810204416, 1019740041, 1053265741, 1972957241, 3339356041, 5914492241, 6886737541, 6388758241, 8902368041, 7858982841, 4942246941, 18439299341, 26639916441

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..38

Michael S. Branicky, Python program for A374141, A374142, and A374143

Eric Weisstein's World of Mathematics, Octagonal Number

Example

a(2) = 1053 = 8 + 1045 = 408 + 645.

Prog

(Python) # see linked program

Crossrefs

Cf. A000567, A093195, A332989, A342326, A374141, A374142.

Sequence in context: A277829 A286396 A174636 * A054344 A372652 A048912

Adjacent sequences: A374140 A374141 A374142 * A374144 A374145 A374146

Keyword

nonn

Author

Ilya Gutkovskiy, Jun 28 2024

Extensions

a(9)-a(29) from Michael S. Branicky, Jun 29 2024

Status

approved