A119035 Triangular numbers composed of digits {0,1,3}.

1, 3, 10, 300, 3003, 10011, 303031, 1010331, 1030330, 1313010, 101111310, 113033130, 1033010331, 11031100311, 11033031331, 31031010003, 111111101310, 313313301003, 10113301131300, 3330130113300130003, 1113011003000100031311, 11013033300110103011310

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119036. See A119033 for a table of cross-references.

Programs

Magma

[t: n in [1..2*10^7] | Set(Intseq(t)) subset {0,1,3} where t is n*(n+1) div 2]; // Vincenzo Librandi, Dec 18 2015

Mathematica

Rest[Select[FromDigits/@Tuples[{0, 1, 3}, 10], IntegerQ[(Sqrt[8 # + 1] - 1)/2] &]] (* Vincenzo Librandi, Dec 18 2015 *)

Formula

a(n) = A000217(A119036(n)). - Tyler Busby, Mar 31 2023

Extensions

a(21)-a(22) from Tyler Busby, Mar 22 2023