A119040 Numbers k such that the k-th triangular number contains only digits {0,1,5}.

1, 4, 5, 10, 14, 100, 101, 141, 173, 458, 1000, 1001, 1005, 1010, 4475, 10000, 10001, 10005, 10010, 10100, 10110, 10114, 14869, 45858, 54873, 100000, 100001, 100005, 100010, 100100, 100101, 101000, 101005, 1000000, 1000001, 1000005, 1000010

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• G. Resta, Tridigital Triangular Numbers

Crossrefs

Cf. A000217, A119039. See A119034 for a table of cross-references.

Programs

Magma

[n: n in [1..2*10^6] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 5]]; // Vincenzo Librandi, Dec 25 2015

Mathematica

Select[Range[2 10^6], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 5}] == {} &] (* Vincenzo Librandi, Dec 25 2015 *)