This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A350927 #39 Jan 30 2022 19:31:56 %S A350927 1,2,4,6,3,9,8,10,5,15,12,14,7,21,16,18,20,22,11,33,24,26,13,39,27,28, %T A350927 30,25,35,32,34,17,51,36,38,19,57,40,42,44,46,23,69,45,48,50,52,54,56, %U A350927 49,63,58,29,87,60,55,65,62,31,93,64,66,68,70,72,74,37,111,75,76,78,80,82,41,123,81 %N A350927 a(1)=1, a(2)=2; for n > 2, a(n) is the smallest unused positive number such that gcd(a(n-1) * |a(n-1) - a(n-2)|, a(n)) > 1. %C A350927 This is likely a permutation of the natural numbers. The sequence shows similar behavior to the EKG sequence A064413. In the first 500000 terms the fixed points are 1, 2, 77, 221, and it is likely no more exist. %H A350927 Scott R. Shannon, <a href="/A350927/a350927.png">Image of the first 10000 terms</a>. The green line is y = n. %e A350927 a(4) = 6 as a(3)*|a(3)-a(2)| = 4*2 = 8, 6 has not been used and gcd(6,8) > 1. %e A350927 a(8) = 10 as a(7)*|a(7)-a(6)| = 8*1 = 8, 10 has not been used and gcd(10,8) > 1. %Y A350927 Cf. A351001, A337136, A064413, A336957, A098550, A089088, A251622. %K A350927 nonn %O A350927 1,2 %A A350927 _Scott R. Shannon_, Jan 28 2022