OFFSET
1,2
COMMENTS
It seems that for n>1, a(2n-1) is always even, which forces a(2n) to be odd. Together, these prevent any further powers of 2 from appearing in the sequence. In fact, it appears that a(2n+1) is always either less than a(2n) or equal to a(2n) + the least prime factor of a(2n); and very rarely is a(2n) anything other than the smallest odd number not yet used (the first instance for n>1 is a(96) = 97 instead of 95). - Franklin T. Adams-Watters, Sep 01 2006
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
PROG
(Haskell)
import Data.List (delete)
a091857 n = a091857_list !! (n-1)
a091857_list = 1 : f 1 1 [2..] where
f 1 z xs = g xs where
g (u:us) = if gcd u z == 1 then u : f 0 u (delete u xs) else g us
f 0 z xs = h xs where
h (v:vs) = if gcd v z /= 1 then v : f 1 v (delete v xs) else h vs
-- Reinhard Zumkeller, Feb 17 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Amarnath Murthy, Mar 13 2004
EXTENSIONS
More terms from Franklin T. Adams-Watters, Sep 01 2006
Data corrected for n > 52 by Reinhard Zumkeller, Feb 17 2015
STATUS
approved