%I #13 Sep 03 2018 02:53:43
%S 4,6,10,33,18,42,48,58,70,82,90,102,110,120,126,140,144,154,150,182,
%T 180,198,200,220,216,228,272,252,280,270,300,306,312,330,336,340,348,
%U 360,390,392,396,400,442,438,468,440,506,480,484,500,486,518,528,540,574,546,570,572,616
%N List of composite numbers in A098550 which appear immediately after a prime.
%H Reinhard Zumkeller, <a href="/A253048/b253048.txt">Table of n, a(n) for n = 1..10000</a>
%H 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 <a href="https://cs.uwaterloo.ca/journals/JIS/VOL18/Sloane/sloane9.html">J. Int. Seq. 18 (2015) 15.6.7</a>.
%t f[lst_] := Block[{k = 4}, While[GCD[lst[[-2]], k] == 1 || GCD[lst[[-1]], k] > 1 || MemberQ[lst, k], k++]; Append[lst, k]];
%t A098550 = Nest[f, {1, 2, 3}, 1000];
%t sp = SequencePosition[A098550, {_?PrimeQ, _?CompositeQ}] [[All, 2]];
%t A098550[[sp]] (* _Jean-François Alcover_, Sep 03 2018, after _Robert G. Wilson v_ in A098550 *)
%o (Haskell)
%o a253048 n = a253048_list !! (n-1)
%o a253048_list = filter ((== 0) . a010051') $ map a253049 [1..]
%o -- _Reinhard Zumkeller_, Dec 30 2014
%Y Cf. A098550. Subsequence of A253049.
%Y Cf. A010051, A251239.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Dec 27 2014