A043104 Numbers k such that 1 and 3 occur juxtaposed in the base-4 representation of k but not of k-1.

7, 13, 23, 28, 39, 45, 52, 61, 71, 77, 87, 92, 103, 109, 112, 135, 141, 151, 156, 167, 173, 180, 189, 199, 205, 208, 231, 237, 244, 253, 263, 269, 279, 284, 295, 301, 308, 317, 327, 333, 343, 348, 359, 365, 368, 391, 397, 407, 412

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, 450}], {0, 1}][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 12 2020 *)

Crossrefs

Cf. A007090.

Sequence in context: A273605 A273641 A214794 * A339112 A340020 A106349

Adjacent sequences: A043101 A043102 A043103 * A043105 A043106 A043107

Keyword

nonn,base

Author

Clark Kimberling

Status

approved