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%I #10 Oct 17 2021 13:04:26
%S 17,71,117,170,217,271,317,371,417,471,517,571,617,671,710,771,817,
%T 871,917,971,1017,1071,1117,1170,1217,1271,1317,1371,1417,1471,1517,
%U 1571,1617,1671,1700,1817,1871,1917,1971,2017,2071
%N Numbers k such that 1 and 7 occur juxtaposed in the base-10 representation of k but not of k-1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n],{1,7}]>0 || SequenceCount[IntegerDigits[n],{7,1}]>0,1,0],{n,2100}],{0,1}][[All,2]] (* _Harvey P. Dale_, Oct 17 2021 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
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