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 A251411 Numbers n such that A098550(n) = n. 3
 1, 2, 3, 4, 12, 50, 86 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS There is a strong conjecture that there are no further terms. See the discussion in the comments in A098550. REFERENCES L. Edson Jeffery, Posting to Sequence Fans Mailing List, Nov 30 2014. LINKS Hans Havermann, Loops and unresolved chains for map n -> A098550(n) trajectories 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. MATHEMATICA max = 100; 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}, max - 3]; Select[Transpose[{Range[max], A098550}], #[[1]] == #[[2]]&][[All, 1]] (* Jean-François Alcover, Sep 05 2018, after Robert G. Wilson v in A098550 *) PROG (Python) from fractions import gcd A251411_list, l1, l2, s, b = [1, 2, 3], 3, 2, 4, {} for n in range(4, 10**4): ....i = s ....while True: ........if not i in b and gcd(i, l1) == 1 and gcd(i, l2) > 1: ............l2, l1, b[i] = l1, i, 1 ............while s in b: ................b.pop(s) ................s += 1 ............if i == n: ................A251411_list.append(n) ............break ........i += 1 # Chai Wah Wu, Dec 03 2014 CROSSREFS Cf. A098550, A251412, A251556. Sequence in context: A053350 A165302 A276530 * A117342 A328210 A303385 Adjacent sequences:  A251408 A251409 A251410 * A251412 A251413 A251414 KEYWORD nonn AUTHOR N. J. A. Sloane, Dec 02 2014 STATUS approved

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Last modified June 15 00:00 EDT 2021. Contains 345041 sequences. (Running on oeis4.)