A119101 Triangular numbers composed of digits {1,2,5}.

1, 15, 21, 55, 1225, 2211, 5151, 15225, 21115, 22155, 151525, 222111, 255255, 11551221, 12552555, 21115251, 22221111, 51151555, 111221155, 251115255, 2222211111, 2552515525, 111251152551, 122515222515, 222222111111, 1125152255151, 2522551111515, 5255121522225

Offset

1,2

Links

Table of n, a(n) for n=1..28.

Giovanni Resta, Tridigital Triangular Numbers

Formula

a(n) = A000217(A119102(n)). - Michel Marcus, Mar 22 2023

Crossrefs

Cf. A000217, A031153, A119102. See A119033 for a table of cross-references.

Sequence in context: A275169 A063176 A083372 * A342806 A190662 A274084

Adjacent sequences: A119098 A119099 A119100 * A119102 A119103 A119104

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

a(26)-a(28) from Tyler Busby, Mar 22 2023

Status

approved