

A091856


Beginning with 1, minimum value such that gcd(a(2n1),a(2n)) = 1, gcd(a(2n),a(2n+1))>1 and a(n) > a(n1).


2



1, 2, 4, 5, 10, 11, 22, 23, 46, 47, 94, 95, 100, 101, 202, 203, 210, 211, 422, 423, 426, 427, 434, 435, 438, 439, 878, 879, 882, 883, 1766, 1767, 1770, 1771, 1778, 1779, 1782, 1783, 3566, 3567, 3570, 3571, 7142, 7143, 7146, 7147, 7154, 7155, 7158, 7159
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OFFSET

1,2


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..264


FORMULA

a(2n) = a(2n1) + 1, a(2n+1) = a(2n) + LeastPrimeFactor(a(2n)).


PROG

(Haskell)
a091856 n = a091856_list !! (n1)
a091856_list = 1 : f 1 1 [2..] where
f s z xs = g xs where
g (u:us) = if gcd u z  s /= 1 then u : f (1  s) u us else g us
 Reinhard Zumkeller, Feb 17 2015


CROSSREFS

Cf. A091857, A020639.
Sequence in context: A018339 A128216 A080735 * A083416 A022770 A141481
Adjacent sequences: A091853 A091854 A091855 * A091857 A091858 A091859


KEYWORD

easy,nonn


AUTHOR

Amarnath Murthy, Mar 13 2004


EXTENSIONS

Edited and extended by Franklin T. AdamsWatters, Dec 26 2006
Typo in data corrected by D. S. McNeil, Aug 17 2010


STATUS

approved



