A119117 Triangular numbers composed of digits {1,3,7}.

1, 3, 171, 1711, 1717731, 17131731, 1313137337331, 117717311713137711, 773113771333731171, 3773733771711731311, 177177371373713177137131, 311733717173773173111771, 3311337711173711371777131, 1173713773733717717113371171

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119118. See A119033 for a table of cross-references.

Formula

a(n) = A000217(A119118(n)).

Extensions

a(14) from Tyler Busby, Mar 28 2023