A026139 a(n) = s(k), where k is the n-th number such that s(j) < s(k) for all j < k, where s = A026136. Also a(n) = 2*t(n) - 1, where t = A026138.

1, 3, 7, 9, 15, 19, 21, 25, 27, 33, 39, 43, 45, 51, 55, 57, 61, 63, 69, 73, 75, 79, 81, 87, 93, 97, 99, 105, 111, 115, 117, 123, 127, 129, 133, 135, 141, 147, 151, 153, 159, 163, 165, 169, 171, 177, 181, 183, 187, 189, 195, 201, 205, 207, 213

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

Records in A026136. - Michael De Vlieger, Aug 27 2021

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.

Crossrefs

Cf. A026138.

Programs

Mathematica

Block[{a, r, s, nn = 108}, a[1] = 1; Do[If[! IntegerQ[a[#1]], Set[a[#1], i], Set[a[#2], i]] & @@ {i - #, i + #} &@ Floor[i/2], {i, 2 nn}]; s = TakeWhile[Array[a[#] &, nn], IntegerQ]; Union@ FoldList[Max, s]] (* Michael De Vlieger, Aug 27 2021 *)

Extensions

Edited by N. J. A. Sloane, Jan 31 2020