A119149 Numbers k such that the k-th triangular number contains only digits {1,7,9}.

1, 13, 18, 58, 586, 1258, 58613, 1350538, 1414213, 59517693, 1398413386, 5996665693, 119976657489461

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base
• more

Comments

Next term exceeds 1.4*10^16.

Links

• G. Resta, Tridigital Triangular Numbers

Crossrefs

Cf. A000217, A119148. See A119034 for a table of cross-references.