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%I #3 Mar 30 2012 18:57:06
%S 1,2,7,5,9,3,10,4,14,6,19,8,23,11,25,12,28,13,31,15,33,16,35,17,38,18,
%T 41,20,43,21,46,22,50,24,53,26,56,27,59,29,62,30,66,32,70,34,73,36,76,
%U 37,79,39,82,40,86,42,89,44,92,45,95,47,97,48,100,49,103,51,106,52,109
%N Inductive sum-and-difference sequence.
%C A permutation of the natural numbers.
%F a(1)=1, a(2)=2 and for n>=3 let F(n)={a(1),a(2),...,a(n)}. For odd n>=3, a(n)=x+y where x,y are the least positive integers not in F(n-1); for even n>=3, a(n)=least positive difference x-y such that x,y are in F(n-1) and x-y is not in F(n-1).
%e a(3)=3+4, a(4)=7-2, a(4)=3+6, a(5)=5-2, a(6)=4+6.
%Y Cf. A117932, A117933.
%K nonn
%O 1,2
%A _Clark Kimberling_, Apr 03 2006
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