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 A043885 Numbers k such that 2 and 3 occur juxtaposed in the base-4 representation of k but not of k+1. 1
 11, 14, 27, 30, 47, 59, 62, 75, 78, 91, 94, 111, 123, 126, 139, 142, 155, 158, 191, 203, 206, 219, 222, 239, 251, 254, 267, 270, 283, 286, 303, 315, 318, 331, 334, 347, 350, 367, 379, 382, 395, 398, 411, 414, 447, 459, 462, 475, 478, 495, 507, 510, 523, 526, 539, 542 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS David A. Corneth, Table of n, a(n) for n = 1..10000 EXAMPLE 27 is in the sequence as 27_10 = 123_4 which has 23 juxtaposed in its base-4 representationand 28_10 = 130_4 does not have 23 juxtaposed in its base-4 representation. - David A. Corneth, Aug 28 2023 MATHEMATICA SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 4], {2, 3}]>0 || SequenceCount[ IntegerDigits[ n, 4], {3, 2}]>0, 1, 0], {n, 500}], {1, 0}][[;; , 1]] (* Harvey P. Dale, Aug 28 2023 *) PROG (PARI) is(n) = {has23juxtaposed(n) && !has23juxtaposed(n+1)} has23juxtaposed(n) = {my(d = digits(n, 4)); for(i = 1, #d-1, if(d[i] == 2 && d[i+1] == 3, return(1)); if(d[i] == 3 && d[i+1] == 2, return(1))); 0} \\ David A. Corneth, Aug 28 2023 CROSSREFS Cf. A007090. Cf. A043880, A043881, A043882, A043883, A043884. Sequence in context: A039282 A045139 A043105 * A326916 A305010 A195818 Adjacent sequences: A043882 A043883 A043884 * A043886 A043887 A043888 KEYWORD nonn,base AUTHOR Clark Kimberling EXTENSIONS More terms from David A. Corneth, Aug 28 2023 STATUS approved

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Last modified September 17 18:39 EDT 2024. Contains 375990 sequences. (Running on oeis4.)