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%I #11 Oct 17 2019 14:26:40
%S 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,
%T 29,30,31,32,33,34,35,37,38,39,40,41,42,43,45,46,50,51,52,53,54,55,56,
%U 57,60,61,62,63,64,65,68,69,70,72,73,75,76,78,79,80,82,83,84,86,87,88
%N Numbers k such that the decimal expansion of (k^2 + k)/2 (the k-th triangular number) contains no pair of consecutive equal digits.
%t Select[Range[0,88],FreeQ[Differences[IntegerDigits[(#^2+#)/2]],0]&] (* _Jayanta Basu_, May 31 2013 *)
%Y Cf. A043096, A000217, A050760.
%K nonn,base
%O 1,3
%A _Patrick De Geest_, Sep 15 1999
%E Name clarified and offset changed to 1 by _Jon E. Schoenfield_, Oct 16 2019
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