A119113 Triangular numbers composed of digits {1,3,5}.

1, 3, 15, 55, 153, 351, 5151, 33153, 35511, 3531153, 3555111, 35133153, 51151555, 51313515, 355311153, 355551111, 1553111511, 5135151153, 5351313331, 15533353153, 35553111153, 35555511111, 153335313531, 155315331153, 315331155153, 355333351555, 1353153151155

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119114. See A119033 for a table of cross-references.

Programs

Mathematica

Select[Accumulate[Range[1000000]],Union[Drop[DigitCount[#], {1,5,2}]]=={0}&]  (* Harvey P. Dale, Apr 16 2011 *)
Table[Select[FromDigits/@Tuples[{1,3,5},n],OddQ[Sqrt[8#+1]]&],{n,12}]//Flatten (* Harvey P. Dale, Aug 02 2022 *)

Formula

a(n) = A000217(A119114(n)). - Michel Marcus, Mar 22 2023

Extensions

a(25)-a(27) from Tyler Busby, Mar 22 2023