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%I #7 Feb 19 2024 18:01:58
%S 22,71,120,154,169,218,267,316,365,414,463,497,512,561,610,659,708,
%T 757,806,840,855,904,953,1002,1051,1078,1149,1183,1198,1247,1296,1345,
%U 1394,1443,1492,1526,1541,1590,1639,1688,1737,1786
%N Numbers n such that string 3,1 occurs in the base 7 representation of n but not of n-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{3,1}]>0,1,0],{n,2000}],{0,1}][[;;,2]] (* _Harvey P. Dale_, Feb 19 2024 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_