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%I #7 Nov 27 2018 20:20:31
%S 17,53,89,107,125,161,197,233,269,305,323,341,377,413,449,485,521,539,
%T 557,593,647,665,701,737,755,773,809,845,881,917,953,971,989,1025,
%U 1061,1097,1133,1169,1187,1205,1241,1277,1313,1349
%N Numbers n such that string 2,5 occurs in the base 6 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,6],{2,5}]>0,1,0],{n,1500}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 27 2018 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_