A169837 EKG sequence started at 3 instead of 2.

3, 6, 2, 4, 8, 10, 5, 15, 9, 12, 14, 7, 21, 18, 16, 20, 22, 11, 33, 24, 26, 13, 39, 27, 30, 25, 35, 28, 32, 34, 17, 51, 36, 38, 19, 57, 42, 40, 44, 46, 23, 69, 45, 48, 50, 52, 54, 56, 49, 63, 60, 55, 65, 70, 58, 29, 87, 66, 62, 31, 93, 72, 64, 68, 74, 37, 111, 75, 78, 76, 80, 82, 41

Offset: 1

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Keywords

• nonn

Comments

A generalization of A064413.

a(n) = A064413(n+1) for n > 43; a(n) = A169849(n) for n > 9. - Reinhard Zumkeller, Jul 04 2014

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Gordon Hamilton, The EKG Sequence and the Tree of Numbers
• Eric Weisstein's World of Mathematics, EKG Sequence
• Index entries for sequences related to EKG sequence

Crossrefs

Cf. A064413, A064417, A169849.

Programs

Haskell

import Data.List (delete)
a169837 n = a169837_list !! (n-1)
a169837_list = 3 : ekg 3 (2 : [4..]) where
   ekg x zs = f zs where
       f (y:ys) = if gcd x y > 1 then y : ekg y (delete y zs) else f ys
-- Reinhard Zumkeller, Jul 04 2014