A119046 Numbers k such that the k-th triangular number contains only digits {0,1,8}.

1, 4, 46, 126, 141, 404, 466, 1541, 4004, 4195, 4666, 12658, 13266, 40004, 41995, 46666, 147024, 400004, 402760, 466666, 1272798, 1327266, 1332666, 4000004, 4666666, 40000004, 46666666, 133272666, 133326666, 148329375, 400000004

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• G. Resta, Tridigital Triangular Numbers

Crossrefs

Cf. A000217, A119045. See A119034 for a table of cross-references.

Programs

Magma

[n: n in [1..4*10^6] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 8]]; // Vincenzo Librandi, Dec 25 2015

Mathematica

Select[Range[2 10^7], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 8}] == {} &] (* Vincenzo Librandi, Dec 25 2015 *)