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 A044005 Numbers k such that 1 and 2 occur juxtaposed in the base-10 representation of k but not of k+1. 1
 12, 21, 112, 129, 219, 221, 312, 321, 412, 421, 512, 521, 612, 621, 712, 721, 812, 821, 912, 921, 1012, 1021, 1112, 1129, 1299, 1312, 1321, 1412, 1421, 1512, 1521, 1612, 1621, 1712, 1721, 1812, 1821, 1912, 1921, 2012, 2021 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 MATHEMATICA With[{j = 1, k = 2}, SequencePosition[Table[If[SequenceCount[IntegerDigits[n], {j, k}] > 0 || SequenceCount[IntegerDigits[n], {k, j}] > 0, 1, 0], {n, 2100}], {1, 0}][[All, 1]]] (* Michael De Vlieger, Aug 27 2021 *) CROSSREFS Sequence in context: A043225 A111066 A201015 * A321771 A225864 A134514 Adjacent sequences:  A044002 A044003 A044004 * A044006 A044007 A044008 KEYWORD nonn,base AUTHOR STATUS approved

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Last modified September 24 22:46 EDT 2021. Contains 347651 sequences. (Running on oeis4.)