A251546 a(n) = smallest even number not in {A098550(1), A098550(2), ..., A098550(n)}.
2, 4, 4, 6, 6, 6, 6, 6, 6, 10, 10, 10, 10, 10, 10, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 24, 24, 30, 30, 30, 30, 30, 30, 38, 38, 40, 40, 40, 40, 40, 40, 40, 46, 46, 46, 46, 46, 46, 46, 46, 54, 54, 54
Offset: 1
Keywords
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..10000
- David L. Applegate, Hans Havermann, Bob Selcoe, Vladimir Shevelev, N. J. A. Sloane, and Reinhard Zumkeller, The Yellowstone Permutation, arXiv preprint arXiv:1501.01669 [math.NT], 2015 and J. Int. Seq. 18 (2015) 15.6.7.
Crossrefs
Programs
-
Haskell
import Data.List ((\\)) a251546 n = head $ [2, 4 ..] \\ filter even (take n a098550_list) -- Reinhard Zumkeller, Dec 19 2014
-
Mathematica
terms = 100; f[lst_List] := Block[{k = 4}, While[GCD[lst[[-2]], k] == 1 || GCD[lst[[-1]], k] > 1 || MemberQ[lst, k], k++]; Append[lst, k]]; A098550 = Nest[f, {1, 2, 3}, terms - 3]; a[1] = 2; a[n_] := a[n] = For[k = a[n-1], True, k += 2, If[FreeQ[A098550[[1;;n]], k], Return[k]]]; Array[a, terms] (* Jean-François Alcover, Aug 01 2018, after Robert G. Wilson v *)
Comments