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 A070802 #4 Oct 15 2013 22:31:19
%S A070802 1,0,4,0,8,0,8,6,12,0,18,0,16,12,20,0,30,0,30,18,20,0,48,8,28,18,40,0,
%T A070802 60,0,44,24,36,18,76,0,40,24,72,0,76,0,60,44,48,0,96,10,66,34,68,0,94,
%U A070802 30,84,42,60,0,150,0,58,66,90,30,116,0,76,42,110,0,164,0,76,72,102,28
%N A070802 a(n)=prevprime[sigma(n)]-nextprime[phi(n)]=A070801(n)-A070800(n).
%F A070802 a(n)=p[Pi(sigma[n])]-p[1+Pi(phi[n])]
%e A070802 n=100:sigma[100]=217,prevprime[217]=211, phi[100]=40,nextprime[40]=41,a(100)=211-41=170. The difference is 0 for odd primes.
%t A070802 Table[Prime[PrimePi[DivisorSigma[1, w]]]- Prime[1+PrimePi[EulerPhi[w]]], {w, 2, 128}]
%Y A070802 Cf. A007917, A007818, A000010, A000203, A000720, A000040, A070800, A070801.
%K A070802 easy,nonn
%O A070802 2,3
%A A070802 _Labos Elemer_, May 08 2002