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 A251237 Indices of even numbers in A098550. 6
 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 27, 29, 31, 33, 35, 37, 39, 41, 44, 46, 48, 50, 52, 54, 56, 58, 60, 63, 65, 67, 69, 71, 73, 75, 77, 80, 82, 84, 86, 89, 91, 93, 95, 97, 99, 102, 104, 106, 108, 110, 112, 115, 117, 119, 121, 123, 125, 128, 130, 133, 135 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A098550(a(n)) mod 2 = 0; a(n+1) > a(n) + 1; there are infinitely many even terms in A098550, for proof: see comment #4 in A098550. 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. MATHEMATICA f[lst_] := Block[{k = 4}, While[GCD[lst[[-2]], k] == 1 || GCD[lst[[-1]], k] > 1 || MemberQ[lst, k], k++]; Append[lst, k]]; Position[Nest[f, {1, 2, 3}, 140], _?EvenQ] // Flatten (* Jean-François Alcover, Oct 01 2018, after Robert G. Wilson v in A098550 *) PROG (Haskell) a251237 n = a251237_list !! (n-1) a251237_list = filter (even . a098550) [1..] CROSSREFS Cf. A098550, A005843, A251238, A251393. First row of array A251716. Sequence in context: A272670 A234521 A085125 * A194402 A134930 A084562 Adjacent sequences:  A251234 A251235 A251236 * A251238 A251239 A251240 KEYWORD nonn AUTHOR Reinhard Zumkeller, Dec 02 2014 STATUS approved

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Last modified October 20 21:31 EDT 2018. Contains 316404 sequences. (Running on oeis4.)