A119140 Triangular numbers composed of digits {1,6,7}.

1, 6, 66, 171, 666, 1176, 1711, 17766, 61776, 67161, 166176, 617716, 7767711, 61677171, 77171676, 161667171, 166777716, 611677776, 66767167176, 77111161116, 171676611666, 617617761166, 1116177116671, 161776717667666676, 1116166667661771771, 6667177116611677771

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers

Crossrefs

Cf. A000217, A053907, A119141. See A119033 for a table of cross-references.

Formula

a(n) = A000217(A119141(n)). - Michel Marcus, Mar 22 2023

Extensions

a(24)-a(26) from Tyler Busby, Mar 22 2023