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 A049586 #23 Sep 08 2022 08:44:58 %S A049586 1,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,3,3,1,1,1,1,1,1,1,1,1,1,1,1,1, %T A049586 1,1,1,5,3,1,1,1,1,3,3,1,1,1,1,1,1,1,1,3,1,1,3,1,1,1,1,1,1,1,1,1,1,1, %U A049586 1,1,1,1,1,1,5,1,1,1,1,3,3,1,1,3,1,1,1,1,1,1,1,3,3,1,1,1,1,1,3,1,1,1,1,1,3 %N A049586 a(n) is the GCD of the cototients (A051953) of n and n+1. %C A049586 Most of the terms are 1. %H A049586 Vincenzo Librandi, <a href="/A049586/b049586.txt">Table of n, a(n) for n = 0..5000</a> %F A049586 a(n) = gcd(n + 1 - phi(n+1), n - phi(n)). %F A049586 a(n) = gcd(A051953(n+1), A051953(n)). %t A049586 Map[GCD @@ Map[# - EulerPhi@ # &, #] &, Partition[Range@ 106, 2, 1]] (* _Michael De Vlieger_, Aug 09 2017 *) %o A049586 (Magma) [GCD((n+1-EulerPhi(n+1)), n-EulerPhi(n)): n in [1..100]]; // _Vincenzo Librandi_, Aug 10 2017 %Y A049586 Cf. A000010, A051953, A058515. %K A049586 nonn %O A049586 0,9 %A A049586 _Labos Elemer_, Dec 28 2000