A043139 Numbers k such that 1 and 4 occur juxtaposed in the base-7 representation of k but not of k-1.

11, 29, 60, 77, 109, 127, 158, 176, 203, 225, 256, 274, 305, 323, 354, 372, 403, 420, 452, 470, 501, 519, 539, 599, 617, 648, 666, 697, 715, 746, 763, 795, 813, 844, 862, 889, 911, 942, 960, 991, 1009, 1040, 1058, 1089, 1106

Offset

1,1

Links

Table of n, a(n) for n=1..45.

Mathematica

SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 7], {1, 4}]>0 || SequenceCount[IntegerDigits[n, 7], {4, 1}]>0, 1, 0], {n, 1200}], {0, 1}][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 04 2020 *)

Crossrefs

Cf. A007093.

Sequence in context: A329403 A171667 A340573 * A043919 A120946 A216296

Adjacent sequences: A043136 A043137 A043138 * A043140 A043141 A043142

Keyword

nonn,base

Author

Clark Kimberling

Status

approved