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

1,2

Links

Table of n, a(n) for n=1..27.

Giovanni Resta, Tridigital Triangular Numbers.

Formula

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

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 *)

Crossrefs

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

Sequence in context: A093925 A117960 A176288 * A286185 A152896 A007973

Adjacent sequences: A119110 A119111 A119112 * A119114 A119115 A119116

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

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

Status

approved