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A050759 Numbers k such that the decimal expansion of (k^2 + k)/2 (the k-th triangular number) contains no pair of consecutive equal digits. 1
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 45, 46, 50, 51, 52, 53, 54, 55, 56, 57, 60, 61, 62, 63, 64, 65, 68, 69, 70, 72, 73, 75, 76, 78, 79, 80, 82, 83, 84, 86, 87, 88 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..72.

MATHEMATICA

Select[Range[0, 88], FreeQ[Differences[IntegerDigits[(#^2+#)/2]], 0]&] (* Jayanta Basu, May 31 2013 *)

CROSSREFS

Cf. A043096, A000217, A050760.

Sequence in context: A118766 A136399 A056167 * A039274 A102487 A102234

Adjacent sequences:  A050756 A050757 A050758 * A050760 A050761 A050762

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Sep 15 1999

EXTENSIONS

Name clarified and offset changed to 1 by Jon E. Schoenfield, Oct 16 2019

STATUS

approved

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Last modified December 7 03:00 EST 2019. Contains 329836 sequences. (Running on oeis4.)