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A099257 a(1)=1, a(n+1) = if a(n)=n then 2*n+1 else smallest number not occurring earlier. 3

%I

%S 1,3,2,4,9,5,6,7,8,10,21,11,12,13,14,15,16,17,18,19,20,22,45,23,24,25,

%T 26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,46,93,47,48,

%U 49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71

%N a(1)=1, a(n+1) = if a(n)=n then 2*n+1 else smallest number not occurring earlier.

%C Permutation of the natural numbers with inverse A099258;

%C a(A033484(n)) = A033484(n);

%C a(A033484(n) + 1) = 2*A033484(n) + 1 = A068156(n).

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

%F a(n) = if n = 3*2^k - 2 then n else (if n = 3*2^k - 1 then 2*n + 1 else n - 1).

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Oct 09 2004

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Last modified May 26 05:25 EDT 2019. Contains 323579 sequences. (Running on oeis4.)