OFFSET
1,2
COMMENTS
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Michael De Vlieger, Log log scatterplot of a(n), n = 1..2^12, showing records in red, local minima in blue, highlighting primes in green and other prime powers in gold.
MATHEMATICA
nn = 72; c[_] = False; Set[{a[1], c[1]}, {1, True}]; u = 2; Do[Set[{j, k}, {a[Ceiling[n/2]], u}]; While[Nand[! c[k], CoprimeQ[j, k]], k++]; Set[{a[n], c[k]}, {k, True}]; If[k == u, While[c[u], u++]], {n, 2, nn}]; Array[a, nn] (* Michael De Vlieger, Oct 28 2022 *)
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
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Sep 02 2004
EXTENSIONS
Typo in definition fixed by Reinhard Zumkeller, Oct 11 2014
STATUS
approved