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

1,2

Links

Table of n, a(n) for n=1..20.

Giovanni Resta, Tridigital Triangular Numbers.

Formula

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

Crossrefs

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

Sequence in context: A225509 A235533 A039369 * A043192 A043972 A226196

Adjacent sequences: A119135 A119136 A119137 * A119139 A119140 A119141

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

a(20) from Tyler Busby, Mar 28 2023

Status

approved