A119148 Triangular numbers composed of digits {1,7,9}.

1, 91, 171, 1711, 171991, 791911, 1717771191, 911977119991, 999999911791, 1771177919779971, 977779999771199191, 17979999719799917971, 7197199171171779119991779991

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base
• more

Comments

a(14) > 10^40. - Tyler Busby, Mar 29 2023

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A119149. See A119033 for a table of cross-references.

Formula

a(n) = A000217(A119149(n)). - Tyler Busby, Mar 29 2023