A043884 Numbers k such that 1 and 3 occur juxtaposed in the base-4 representation of k but not of k+1.

7, 13, 23, 31, 39, 45, 55, 61, 71, 77, 87, 95, 103, 109, 127, 135, 141, 151, 159, 167, 173, 183, 189, 199, 205, 223, 231, 237, 247, 253, 263, 269, 279, 287, 295, 301, 311, 317, 327, 333, 343, 351, 359, 365, 383, 391, 397, 407, 415

Offset

1,1

Links

Table of n, a(n) for n=1..49.

Mathematica

SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 4], {1, 3}]>0 || SequenceCount[IntegerDigits[n, 4], {3, 1}]>0, 1, 0], {n, 500}], {1, 0}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 13 2020 *)

Crossrefs

Cf. A007090.

Sequence in context: A293657 A048449 A147812 * A129727 A275897 A227786

Adjacent sequences: A043881 A043882 A043883 * A043885 A043886 A043887

Keyword

nonn,base

Author

Clark Kimberling

Status

approved