A119133 Numbers k such that the k-th triangular number contains only digits {1,5,6}.

1, 3, 5, 10, 11, 33, 36, 101, 105, 114, 333, 336, 471, 1011, 1063, 1141, 1769, 3333, 3336, 3363, 3366, 5588, 5773, 10114, 10541, 11096, 11411, 15241, 33333, 33336, 33363, 33366, 33663, 56773, 111010, 174101, 333333, 333336, 333363, 333366

Offset

1,2

Links

Table of n, a(n) for n=1..40.

G. Resta, Tridigital Triangular Numbers

Mathematica

(Sqrt[8#+1]-1)/2&/@Select[Flatten[Table[FromDigits/@Tuples[{1, 5, 6}, n], {n, 11}]], OddQ[Sqrt[8#+1 ]]&] (* Harvey P. Dale, Nov 02 2014 *)

Crossrefs

Cf. A000217, A119132. See A119034 for a table of cross-references.

Sequence in context: A067230 A321793 A075741 * A284959 A336531 A285415

Adjacent sequences: A119130 A119131 A119132 * A119134 A119135 A119136

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Status

approved