A322045 Triangular numbers that are 2-digit-repblocks.

10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 5050, 5151

Offset: 1

Author

N. J. A. Sloane, Dec 07 2018

Keywords

• nonn
• fini
• full
• base

Links

• Bir Kafle, Florian Luca, and Alain Togbé, Triangular repblocks, The Fibonacci Quarterly, 56:4 (2018), 325-328.

Crossrefs

Cf. A000217, A010785, A045914.

Programs

Mathematica

Select[Union[Flatten[Table[FromDigits[PadRight[{}, n, k], 100], {n, 3}, {k, 10, 99}]]], IntegerQ[Sqrt[8*# + 1]] &] (* Amiram Eldar, Mar 07 2025, after Harvey P. Dale at A045914 *)