A119053 Triangular numbers composed of digits {0,2,6}.

6, 66, 666, 66066, 600060, 6626620, 2620626606, 2200022662006, 626622226002066066, 66006260060666006026, 20066002660020662200026, 222220220206620206202066, 22222002022666602062066226, 66222600026062602006000600, 20666666202602626260022660266

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Comments

a(16) > 10^40. - Tyler Busby, Mar 28 2023

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119054. See A119033 for a table of cross-references.

Programs

Mathematica

Select[Flatten[FromDigits /@ Tuples[{0, 2, 6}, 13]], OddQ[ Sqrt[ 8 # + 1]] &] //Rest (* The program generates the first 8 terms of the sequence. *) (* Harvey P. Dale, Sep 26 2023 *)

Formula

a(n) = A000217(A119054(n))

Extensions

a(14)-a(15) from Max Alekseyev, Aug 26 2013