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

1,1

Links

Table of n, a(n) for n=1..23.

Giovanni Resta, Tridigital Triangular Numbers

Formula

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

Mathematica

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

Crossrefs

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

Sequence in context: A075575 A073655 A119222 * A119079 A119220 A119218

Adjacent sequences: A119161 A119162 A119163 * A119165 A119166 A119167

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

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

Status

approved