Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #8 Mar 21 2019 21:34:57
%S 41,90,139,188,237,286,335,384,433,482,531,580,629,678,727,776,825,
%T 874,923,972,1021,1070,1119,1168,1217,1266,1315,1364,1413,1462,1511,
%U 1560,1609,1658,1707,1756,1805,1854,1903,1952,2001
%N Numbers n such that string 5,6 occurs in the base 7 representation of n but not of n-1.
%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/NonRecursions.html">Non Recursions</a>
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{5,6}] >0,1,0],{n,2500}],{0,1}][[All,2]] (* _Harvey P. Dale_, Mar 21 2019 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_