login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A091856 Beginning with 1, minimum value such that gcd(a(2n-1),a(2n)) = 1, gcd(a(2n),a(2n+1))>1 and a(n) > a(n-1). 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

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

PROG

(Haskell)

a091856 n = a091856_list !! (n-1)

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. Adams-Watters, Dec 26 2006

Typo in data corrected by D. S. McNeil, Aug 17 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 17 19:58 EST 2017. Contains 294834 sequences.