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 A163374 #21 Sep 08 2022 08:45:46 %S A163374 1,1,2,2,2,2,3,2,3,2,3,2,4,3,3,3,2,3,4,3,4,3,3,3,4,4,4,4,4,3,4,2,4,2, %T A163374 4,4,3,4,4,2,4,4,4,4,4,3,3,2,4,4,4,4,4,4,4,4,3,4,3,2,6,4,3,4,4,4,4,4, %U A163374 4,4,4,4,6,3,4,3,6,4,4,4,4,4,3,4,2,4 %N A163374 a(n) = tau(tau(phi(n))). %H A163374 Harvey P. Dale, <a href="/A163374/b163374.txt">Table of n, a(n) for n = 1..1000</a> %F A163374 a(n) = A000005(A000005(A000010(n))) = A000005(A062821(n)) = A010553(A000010(n)). %e A163374 tau(tau(phi(7))) = tau(tau(6)) = tau(4) = 3. Thus a(7) = 3. - _Derek Orr_, Jul 27 2014 %t A163374 DivisorSigma[0,DivisorSigma[0,EulerPhi[Range[90]]]] (* _Harvey P. Dale_, Mar 25 2016 *) %o A163374 (Magma) [NumberOfDivisors(NumberOfDivisors(EulerPhi(n))): n in [1..100]]; // _Vincenzo Librandi_, Jul 27 2014 %o A163374 (PARI) a(n)=sigma(sigma(eulerphi(n),0),0); \\ _Derek Orr_, Jul 27 2014 %Y A163374 Cf. A000005 (tau), A000010 (phi), A010553, A062821. %K A163374 nonn,easy %O A163374 1,3 %A A163374 _Jaroslav Krizek_, Jul 25 2009 %E A163374 More terms from _Vincenzo Librandi_, Jul 27 2014