A026184 a(n) = (1/3)*s(n), where s(n) is the n-th multiple of 3 in A026136.

1, 3, 5, 2, 7, 9, 11, 4, 13, 15, 17, 6, 19, 21, 23, 8, 25, 27, 29, 10, 31, 33, 35, 12, 37, 39, 41, 14, 43, 45, 47, 16, 49, 51, 53, 18, 55, 57, 59, 20, 61, 63, 65, 22, 67, 69, 71, 24, 73, 75, 77, 26, 79, 81, 83, 28, 85, 87, 89, 30, 91, 93, 95

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

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.
• Index entries for linear recurrences with constant coefficients, signature (0,0,0,2,0,0,0,-1).

Crossrefs

Cf. A026136, A026185.

Programs

Mathematica

Block[{a, r, s, nn = 141}, a[1] = 1; Do[If[! IntegerQ[a[#1]], Set[a[#1], i], Set[a[#2], i]] & @@ {i - #, i + #} &@ Floor[i/2], {i, 2 nn}]; Select[TakeWhile[Array[a[#] &, nn], IntegerQ], Mod[#, 3] == 0 &]/3] (* Michael De Vlieger, Aug 27 2021 *)
LinearRecurrence[{0,0,0,2,0,0,0,-1},{1,3,5,2,7,9,11,4},70] (* Harvey P. Dale, Sep 25 2024 *)

Formula

a(4*n) = 2*n, a(4*n+1) = 6*n+1, a(4*n+2) = 6*n+3, a(4*n+3) = 6*n+5 . - Philippe Deléham, Nov 02 2023

Extensions

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