A026222 - 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

A026222

Numbers k such that A026136(k) = A026142(k).

1, 3, 9, 15, 24, 27, 33, 42, 45, 51, 60, 69, 72, 78, 81, 87, 96, 99, 105, 114, 123, 126, 132, 135, 141, 150, 153, 159, 168, 177, 180, 186, 195, 204, 207, 213, 216, 222, 231, 234, 240, 243, 249, 258, 261, 267, 276, 285, 288, 294, 297

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

OFFSET

1,2

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

F. M. Dekking, Permutations of N generated by left-right filling algorithms, arXiv:2001.08915 [math.CO], 2020.

MATHEMATICA

Block[{nn = 10^3, a, b, s, t}, a[1] = b[1] = 1; Do[If[! IntegerQ[a[#1]], Set[a[#1], i], Set[a[#2], i]] & @@ {i - #, i + #} &@ Floor[i/2], {i, nn}]; s = TakeWhile[Array[a[#] &, nn], IntegerQ]; Do[If[! IntegerQ[b[#1]], Set[b[#1], i], Set[b[#2], i]] & @@ {i - #, i + #} &@ Floor[(i + 1)/2], {i, nn}]; t = TakeWhile[Array[b[#] &, nn], IntegerQ]; Select[Range@ Min[Last /@ {s, t}], s[[#]] == t[[#]] &]] (* Michael De Vlieger, Apr 21 2020 *)

CROSSREFS

Sequence in context: A139419 A323031 A058972 * A192720 A357167 A099989

Adjacent sequences: A026219 A026220 A026221 * A026223 A026224 A026225

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved