A119138 Triangular numbers composed of digits {1,5,9}.

1, 15, 55, 91, 595, 5151, 5995, 9591, 1511191, 51151555, 195911115, 511151999595, 519191199555, 555595555515, 595151955555, 591915955919511, 15995115959551911, 159955559191119511, 9199995595111955111955555, 1559111919555519991599911911

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119139. See A119033 for a table of cross-references.

Formula

a(n) = A000217(A119139(n)). - Tyler Busby, Mar 28 2023

Extensions

a(20) from Tyler Busby, Mar 28 2023