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 A070817 #12 Mar 21 2020 16:37:48
%S A070817 -1,0,0,1,0,2,1,3,0,4,3,4,5,6,6,6,6,8,7,6,0,10,7,10,10,11,7,13,10,14,
%T A070817 11,15,14,15,15,16,16,18,15,18,14,17,19,12,0,22,17,20,23,23,13,24,22,
%U A070817 25,25,22,0,28,25,26,28,30,29,28,22,32,23,32,28,33,33,34,32,35,33,36,26,38,37,36,0,39,40,36,36,39,33,42,42,35,41,24
%N A070817 a(n) = floor(n/2) - gpf(phi(n)), where gpf(n) is the largest prime factor of n.
%F A070817 a(n) = A004526(n) - A068211(n) = A004526(n) - A006530(A000010(n)).
%F A070817 If n is a safe prime, then a(n)=0.
%e A070817 For n=3, floor(3/2) = 1, phi(3) = 2, gpf(2) = 2, a(3) = 1 - 2 = -1.
%e A070817 For n=107, floor(107/2) = 53, phi(107) = 2*53, gpf(106) = 53, a(107) = 53 - 53 = 0.
%e A070817 For n=128, floor(128/2) = 64, gpf(phi(128)) = gpf(64) = 2, a(128) = 64 - 2 = 62.
%t A070817 mf[x_] := Part[Reverse[Flatten[FactorInteger[x]]], 2] Table[Floor[n/2//N]-mf[EulerPhi[n]], {w, 3, 128}]
%Y A070817 Cf. A000010, A004526, A005384, A005385, A006530, A068211.
%K A070817 easy,sign
%O A070817 3,6
%A A070817 _Labos Elemer_, May 10 2002