A346386 Triangular numbers that are sum of squares of two distinct triangular numbers.

1, 10, 36, 45, 136, 325, 666, 820, 1225, 2080, 3321, 5050, 7381, 10440, 11026, 14365, 18721, 19306, 25425, 32896, 41905, 52650, 65341, 80200, 90100, 97461, 101025, 117370, 140185, 166176, 195625, 197506, 228826, 266085, 307720, 314821, 354061, 405450, 454581, 462241

Offset

1,2

Links

Table of n, a(n) for n=1..40.

Example

136, 10 and 6 are triangular numbers and 136 = 10^2 + 6^2 so 136 is a term.
820, 28 and 6 are triangular numbers and 820 = 28^2 + 6^2 so 820 is a term.

Mathematica

m = 50; t = Accumulate[Range[0, m]]; Select[Union[Plus @@@ Subsets[t^2, {2}]], # <= t[[-1]]^2 && IntegerQ @ Sqrt[8*# + 1] &] (* Amiram Eldar, Jul 16 2021 *)

Crossrefs

Cf. A000217, A004431, A037270, A073613.

Sequence in context: A223305 A176575 A073613 * A117404 A359959 A309783

Adjacent sequences: A346383 A346384 A346385 * A346387 A346388 A346389

Keyword

nonn

Author

Metin Sariyar, Jul 14 2021

Status

approved