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Lexicographically earliest permutation of the natural numbers such that gcd(s(k-1)+1, a(k)) greater than gcd(s(k-1), a(k)+1), where s is the sum of preceding terms (A121712); a(1)=1.
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%I #11 Oct 18 2019 00:18:55

%S 1,2,4,8,6,10,12,11,15,5,3,9,18,14,7,16,22,20,23,21,19,13,24,26,25,30,

%T 35,28,32,34,36,38,40,42,39,52,33,27,45,46,48,44,41,50,43,54,56,58,60,

%U 62,55,49,51,57,63,17,64,66,61,31,68,65,69,59,37,70,72,76,53,47,74,78

%N Lexicographically earliest permutation of the natural numbers such that gcd(s(k-1)+1, a(k)) greater than gcd(s(k-1), a(k)+1), where s is the sum of preceding terms (A121712); a(1)=1.

%C gcd(A121712(n-1)+1, a(n)) > gcd(A121712(n-1), a(n)+1);

%C inverse: A121713; fixed points: A121716;

%C a(a(n)) = A121714(n).

%H <a href="/index/Ga#gcd">Index entries for sequences related to GCD's</a>.

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

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Aug 18 2006