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.
Index entries for linear recurrences with constant coefficients, signature (0,0,0,2,0,0,0,-1).
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
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 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Edited by N. J. A. Sloane, Jan 31 2020
STATUS
approved