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

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

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..13.

Giovanni Resta, Tridigital Triangular Numbers.

Formula

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

Crossrefs

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

Sequence in context: A225908 A159961 A113530 * A166059 A226683 A370053

Adjacent sequences: A119145 A119146 A119147 * A119149 A119150 A119151

Keyword

nonn,base,more

Author

Giovanni Resta, May 10 2006

Status

approved