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 A318830 #6 Sep 10 2018 06:10:56 %S A318830 0,0,0,1,0,1,0,3,4,3,0,3,0,5,6,7,0,5,0,7,8,9,0,7,16,11,16,9,0,7,0,15, %T A318830 16,15,22,11,0,17,22,15,0,11,0,19,20,21,0,15,36,19,30,21,0,17,38,23, %U A318830 32,27,0,15,0,29,34,31,32,15,0,31,40,21,0,23,0,35,38,33,56,23,0,31,52,39,0,23,60,41,54,39,0,23,54,43 %N A318830 a(n) = phi(n) - gcd(phi(n), n-1). %H A318830 Antti Karttunen, <a href="/A318830/b318830.txt">Table of n, a(n) for n = 1..65537</a> %F A318830 a(n) = A000010(n) - A049559(n) = phi(n) - gcd(phi(n), n-1). %F A318830 a(n) = A318827(n) - A051953(n). %o A318830 (PARI) %o A318830 A049559(n) = gcd(eulerphi(n), n-1); \\ From A049559. %o A318830 A318830(n) = (eulerphi(n)-A049559(n)); %Y A318830 Cf. A000010, A049558, A051953, A318827. %K A318830 nonn %O A318830 1,8 %A A318830 _Antti Karttunen_, Sep 09 2018