



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
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internal format)



OFFSET

1,1


COMMENTS

A251416(n) = Min{a(n), A251549(n)}.  Reinhard Zumkeller, Dec 19 2014


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.


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[n1], True, k += 2, If[FreeQ[A098550[[1;; n]], k], Return[k]]];
Array[a, terms] (* JeanFrançois Alcover, Aug 01 2018, after Robert G. Wilson v *)


PROG

(Haskell)
import Data.List ((\\))
a251546 n = head $ [2, 4 ..] \\ filter even (take n a098550_list)
 Reinhard Zumkeller, Dec 19 2014


CROSSREFS

Cf. A098550, A247253, A251416, A251417, A251547, A251548, A251549, A251550, A251551, A251552.
See also A251557, A251558, A251559.
Sequence in context: A074325 A058249 A058043 * A282894 A162550 A191682
Adjacent sequences: A251543 A251544 A251545 * A251547 A251548 A251549


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Dec 18 2014


STATUS

approved



