A119112 Numbers k such that the k-th triangular number contains only digits {1,3,4}.

1, 2, 53, 258, 25746, 53746, 161946, 7930238, 14927378, 29810546, 4714751561, 25742623453, 94268917816334704578

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base
• more

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119111. See A119034 for a table of cross-references.

Programs

Mathematica

(Sqrt[8#+1]-1)/2&/@Table[Select[FromDigits/@Tuples[{1,3,4},n],OddQ[ Sqrt[ 8#+1]]&],{n,21}]//Flatten (* Harvey P. Dale, Jul 09 2017 *)

Extensions

a(13) from Tyler Busby, Mar 30 2023