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A098311 Smallest number not occurring earlier and coprime to a(ceil(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

Index entries for sequences that are permutations of the natural numbers

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 * A230086 A227082 A227142

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 November 14 19:59 EST 2019. Contains 329128 sequences. (Running on oeis4.)