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A210770 a(1) = 1, a(2) = 2; for n > 1, a(2*n+2) = smallest number not yet seen, a(2*n-1) = a(2*n) + a(2*n+2). 5

%I

%S 1,2,5,3,7,4,10,6,14,8,17,9,20,11,23,12,25,13,28,15,31,16,34,18,37,19,

%T 40,21,43,22,46,24,50,26,53,27,56,29,59,30,62,32,65,33,68,35,71,36,74,

%U 38,77,39,80,41,83,42,86,44,89,45,92,47,95,48,97,49,100

%N a(1) = 1, a(2) = 2; for n > 1, a(2*n+2) = smallest number not yet seen, a(2*n-1) = a(2*n) + a(2*n+2).

%C Permutation of natural numbers with inverse A210771.

%H Reinhard Zumkeller, <a href="/A210770/b210770.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Per#IntegerPermutation"> Index entries for sequences that are permutations of the natural numbers</a>

%F a(2*n-1) = A022441(n-1); a(2*n) = A055562(n-1).

%o (Haskell)

%o import Data.List (delete)

%o a210770 n = a210770_list !! (n-1)

%o a210770_list = 1 : 2 : f 1 2 [3..] where

%o f u v (w:ws) = u' : w : f u' w (delete u' ws) where u' = v + w

%Y Cf. A064736.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Mar 25 2012

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Last modified August 13 22:09 EDT 2020. Contains 336456 sequences. (Running on oeis4.)