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Numbers k such that 1 and 2 occur juxtaposed in the base-5 representation of k but not of k-1.
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%I #10 Jan 14 2022 18:18:32

%S 7,11,32,35,55,61,82,86,107,111,132,136,157,160,175,207,211,232,236,

%T 257,261,275,305,311,332,336,357,361,382,386,407,410,430,436,457,461,

%U 482,486,507,511,532,535,555,561,582,586,607,611

%N Numbers k such that 1 and 2 occur juxtaposed in the base-5 representation of k but not of k-1.

%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,5],{1,2}]>0 || SequenceCount[IntegerDigits[n,5],{2,1}]>0,1,0],{n,700}],{0,1}][[All,2]] (* _Harvey P. Dale_, Jan 14 2022 *)

%Y Cf. A007091.

%K nonn,base

%O 1,1

%A _Clark Kimberling_