A374807 a(n) is the smallest number which can be represented as the sum of 4 distinct nonzero triangular numbers in exactly n ways, or -1 if no such number exists.

20, 38, 47, 64, 73, 92, 97, 110, 127, 115, 130, 164, 185, 172, 208, 157, 199, 235, 247, 232, 220, 272, 277, 304, 280, 361, 262, 307, 319, 391, 322, 292, 495, 415, 337, 367, 370, 382, 478, 482, 412, 409, 445, 430, 467, 500, 427, 532, 493

Offset

1,1

Links

Table of n, a(n) for n=1..49.

Eric Weisstein's World of Mathematics, Triangular Number

Example

a(3) = 47 = 1 + 3 + 15 + 28 = 1 + 10 + 15 + 21 = 3 + 6 + 10 + 28.

Crossrefs

Cf. A000217, A025417, A342326, A374806.

Sequence in context: A294736 A378158 A217427 * A345339 A165442 A242532

Adjacent sequences: A374804 A374805 A374806 * A374808 A374809 A374810

Keyword

nonn

Author

Ilya Gutkovskiy, Jul 20 2024

Status

approved