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A180199 a(n) = A180201(A180201(n)).

%I A180199 #9 Dec 11 2020 17:35:01
%S A180199 0,1,2,3,4,5,6,7,9,8,11,10,12,13,14,15,19,18,17,16,22,23,20,21,25,24,
%T A180199 27,26,28,29,30,31,39,38,37,36,34,35,32,33,45,44,47,46,40,41,42,43,51,
%U A180199 50,49,48,54,55,52,53,57,56,59,58,60,61,62,63,79,78,77,76,74,75,72,73,69
%N A180199 a(n) = A180201(A180201(n)).
%C A180199 Permutation of the natural numbers with inverse A180198;
%C A180199 a(A180200(n)) = A180200(a(n)) = A180201(n);
%C A180199 a(A075427(n)) = A075427(n).
%H A180199 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%o A180199 (R)
%o A180199 nmax <- 31 # by choice
%o A180199 a <- 1:3
%o A180199 for(n in 1:nmax) for(k in 0:3){
%o A180199 if(n %% 2 == 0) a[4*n + k] <- 2*a[2*n + (k == 2 | k == 3)] + (k == 0 | k == 2)
%o A180199 else            a[4*n + k] <- 2*a[2*n + (k == 2 | k == 3)] + (k == 1 | k == 3)
%o A180199 }
%o A180199 (a <- c(0,a))
%o A180199 # _Yosu Yurramendi_, Oct 25 2020
%K A180199 nonn
%O A180199 0,3
%A A180199 _Reinhard Zumkeller_, Aug 15 2010