A119085 Triangular numbers composed of digits {0,5,9}.

55, 595, 990, 5050, 5995, 500500, 50005000, 50909095, 50999950, 505000090, 5000050000, 500000500000, 500999999500, 955909595955, 9055595509950, 50000005000000, 59000000095590, 95595999550590, 5000000050000000, 5000990099009950, 5000990999099095

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A058448, A119086. See A119033 for a table of cross-references.

Programs

Mathematica

Rest[Select[FromDigits/@Tuples[{0,5,9},16],OddQ[Sqrt[8#+1]]&]] (* Harvey P. Dale, Apr 14 2019 *)

Formula

a(n) = A000217(A119086(n)). - Tyler Busby, Mar 31 2023

Extensions

a(20)-a(21) from Tyler Busby, Mar 23 2023