A253048 List of composite numbers in A098550 which appear immediately after a prime.

4, 6, 10, 33, 18, 42, 48, 58, 70, 82, 90, 102, 110, 120, 126, 140, 144, 154, 150, 182, 180, 198, 200, 220, 216, 228, 272, 252, 280, 270, 300, 306, 312, 330, 336, 340, 348, 360, 390, 392, 396, 400, 442, 438, 468, 440, 506, 480, 484, 500, 486, 518, 528, 540, 574, 546, 570, 572, 616

Offset: 1

Author

N. J. A. Sloane, Dec 27 2014

Keywords

• nonn

Links

• Reinhard Zumkeller, 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, 2015 and J. Int. Seq. 18 (2015) 15.6.7.

Crossrefs

Cf. A098550. Subsequence of A253049.

Cf. A010051, A251239.

Programs

Haskell

a253048 n = a253048_list !! (n-1)
a253048_list = filter ((== 0) . a010051') $ map a253049 [1..]
-- Reinhard Zumkeller, Dec 30 2014

Mathematica

f[lst_] := 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}, 1000];
sp = SequencePosition[A098550, {?PrimeQ, ?CompositeQ}] [[All, 2]];
A098550[[sp]] (* Jean-François Alcover, Sep 03 2018, after Robert G. Wilson v in A098550 *)