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A119115
Triangular numbers composed of digits {1,3,6}.
2
1, 3, 6, 36, 66, 136, 666, 13366, 333336, 6631661361, 113113613161, 663363661366, 16116313316131, 633161111666331, 633613661136316, 1331116613613361, 33311633636366361, 663661636336331361, 61163111131316636331, 6313111611636313666666, 1616111661666616161331131
OFFSET
1,2
FORMULA
a(n) = A000217(A119116(n)). - Michel Marcus, Mar 22 2023
MATHEMATICA
Table[Select[FromDigits/@Tuples[{1, 3, 6}, n], OddQ[Sqrt[8#+1]]&], {n, 18}]//Flatten (* Harvey P. Dale, Sep 18 2017 *)
CROSSREFS
Cf. A000217, A053893, A119116. See A119033 for a table of cross-references.
Sequence in context: A019467 A106128 A119186 * A079653 A119063 A119154
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, May 10 2006
EXTENSIONS
a(19)-a(21) from Tyler Busby, Mar 22 2023
STATUS
approved