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 A098311 Smallest number not occurring earlier and coprime to a(ceiling(n/2)); a(1)=1. 4
 1, 2, 3, 5, 4, 7, 6, 8, 9, 11, 10, 12, 13, 17, 15, 19, 14, 16, 18, 20, 21, 23, 25, 29, 22, 24, 26, 27, 28, 31, 30, 32, 33, 37, 35, 39, 41, 43, 47, 49, 34, 38, 36, 40, 42, 44, 45, 46, 51, 53, 55, 59, 57, 61, 50, 52, 65, 67, 48, 54, 71, 73, 63, 69, 56, 58, 60, 62, 64, 66, 68, 70 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(2*n) > a(2*n-1); permutation of the natural numbers with inverse A098313: A098312(n) = a(a(n)). LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 PROG (Haskell) import Data.List ((\\)) a098311 n = a098311_list !! (n-1) a098311_list = 1 : ys where    ys = 2 : f ys [3..] where         f (v:vs) ws = us ++ f vs (ws \\ us) where           us = take 2 \$ filter ((== 1) . (gcd v)) ws -- Reinhard Zumkeller, Oct 11 2014 CROSSREFS Sequence in context: A160051 A082746 A098313 * A342265 A230086 A333404 Adjacent sequences:  A098308 A098309 A098310 * A098312 A098313 A098314 KEYWORD nonn AUTHOR Reinhard Zumkeller, Sep 02 2004 EXTENSIONS Typo in definition fixed by Reinhard Zumkeller, Oct 11 2014 STATUS approved

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Last modified June 19 03:36 EDT 2021. Contains 345125 sequences. (Running on oeis4.)