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A169849 EKG sequence started at 9 instead of 2.

%I A169849 #8 Feb 16 2025 08:33:11
%S A169849 9,3,6,2,4,8,10,5,15,12,14,7,21,18,16,20,22,11,33,24,26,13,39,27,30,
%T A169849 25,35,28,32,34,17,51,36,38,19,57,42,40,44,46,23,69,45,48,50,52,54,56,
%U A169849 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
%N A169849 EKG sequence started at 9 instead of 2.
%C A169849 A generalization of A064413.
%C A169849 a(n) = A064413(n+1) for n > 43; a(n) = A169837(n) for n > 9. - _Reinhard Zumkeller_, Jul 04 2014
%H A169849 Reinhard Zumkeller, <a href="/A169849/b169849.txt">Table of n, a(n) for n = 1..10000</a>
%H A169849 Gordon Hamilton, <a href="http://www.youtube.com/watch?v=yd2jr30K2R4">The EKG Sequence and the Tree of Numbers</a>
%H A169849 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/EKGSequence.html">EKG Sequence</a>
%H A169849 <a href="/index/Ed#EKG">Index entries for sequences related to EKG sequence</a>
%o A169849 (Haskell)
%o A169849 import Data.List (delete)
%o A169849 a169849 n = a169849_list !! (n-1)
%o A169849 a169849_list = 9 : ekg 9 (delete 9 [2..]) where
%o A169849    ekg x zs = f zs where
%o A169849        f (y:ys) = if gcd x y > 1 then y : ekg y (delete y zs) else f ys
%o A169849 -- _Reinhard Zumkeller_, Jul 04 2014
%Y A169849  Cf. A064413, A064417, A169837.
%K A169849 nonn
%O A169849 1,1
%A A169849 _T. D. Noe_ and _N. J. A. Sloane_, Jun 02 2010