A119164 Triangular numbers composed of digits {2,5,6}.

6, 55, 66, 666, 2556, 5565, 6555, 26565, 255255, 2265256, 5656566, 55656525, 525252666, 2665266555, 2666226566655, 6655522556665, 56625555222225, 265556626652565, 555665666566566, 2626662552255225, 6225222656552266, 26256252552656556, 652265255255252222566

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers

Crossrefs

Cf. A000217, A030484, A119165. See A119033 for a table of cross-references.

Programs

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{2,5,6},n],OddQ[Sqrt[8#+1]]&],{n,16}]] (* Harvey P. Dale, Nov 03 2015 *)

Formula

a(n) = A000217(A119165(n)).

Extensions

a(22)-a(23) from Tyler Busby, Mar 24 2023