A043104 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

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

(list; graph; refs; listen; history; text; internal format)

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