A119121 Triangular numbers composed of digits {1,3,9}.

1, 3, 91, 193131, 9939111, 119993391339919111, 199913191913191191, 399139119131339931, 139191313119199339131, 1313933311991311991139331, 3131199393919119319199931, 31313993393319311993391131311, 1191131333139133131313199933931

Offset

1,2

Links

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

Giovanni Resta, Tridigital Triangular Numbers.

Formula

a(n) = A000217(A119122(n)).

Crossrefs

Cf. A000217, A119122. See A119033 for a table of cross-references.

Sequence in context: A331672 A213978 A318129 * A213987 A297479 A116161

Adjacent sequences: A119118 A119119 A119120 * A119122 A119123 A119124

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

a(13) from Tyler Busby, Mar 28 2023

Status

approved