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 A163379 #8 Dec 21 2016 02:43:13 %S A163379 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,2,1,1,1,1, %T A163379 1,2,1,1,1,2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,1,1,1,2,1,1,1,2,1,2,1,1, %U A163379 1,2,1,2,1,1,1,1,1,2,1,2,2,1,1,2,1,1,1,2,1,2,1,1,1,1,1,2 %N A163379 a(n) = phi(phi(tau(n))). %H A163379 G. C. Greubel, <a href="/A163379/b163379.txt">Table of n, a(n) for n = 1..1000</a> %F A163379 a(n) = A000010(A000010(A000005(n))) = A000010(A163109(n)) = A010554(A000005(n)). %t A163379 EulerPhi[EulerPhi[DivisorSigma[0, Range[100]]]] (* _G. C. Greubel_, Dec 20 2016 *) %o A163379 (PARI) vector(100, n, eulerphi(eulerphi(numdiv(n)))) \\ _G. C. Greubel_, Dec 20 2016 %Y A163379 Cf. A000005, A000010, A010554, A163109. %K A163379 nonn %O A163379 1,16 %A A163379 _Jaroslav Krizek_, Jul 25 2009 %E A163379 More terms added by _G. C. Greubel_, Dec 20 2016