%I
%S 5,17,23,32,53,59,71,77,86,98,104,113,161,167,179,185,194,215,221,233,
%T 239,248,260,266,275,296,302,314,320,329,341,347,356,485,491,503,509,
%U 518,539,545,557,563,572,584,590,599,647,653
%N Numbers n such that string 1,2 occurs in the base 3 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,3],{1,2}]>0,1,0],{n,700}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Mar 19 2018 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
