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 A163370 #16 Sep 08 2022 08:45:46 %S A163370 1,1,2,2,6,2,4,6,4,6,6,6,12,4,8,8,30,4,24,8,12,6,12,8,12,12,24,12,24, %T A163370 8,24,30,12,30,16,12,72,24,16,30,24,12,32,12,16,12,24,30,32,12,36,16, %U A163370 42,24,24,16,72,24,24,30,48,24,72,36,60,12,48,36,24,16 %N A163370 a(n) = phi(sigma(phi(n))). %C A163370 a(n) = A000010(A000203(A000010(n))) = A000010(A062402(n)) = A062401(A000010(n)). %H A163370 G. C. Greubel, <a href="/A163370/b163370.txt">Table of n, a(n) for n = 1..1000</a> %p A163370 with(numtheory): A163370:=n->phi(sigma(phi(n))): seq(A163370(n), n=1..100); # _Wesley Ivan Hurt_, Dec 19 2016 %t A163370 EulerPhi[DivisorSigma[1,EulerPhi[Range[80]]]] (* _Harvey P. Dale_, Dec 24 2012 *) %o A163370 (PARI) vector(50, n, eulerphi(sigma(eulerphi(n)))) \\ _G. C. Greubel_, Dec 19 2016 %o A163370 (Magma) [EulerPhi(SumOfDivisors(EulerPhi(n))): n in [1..80]]; // _Vincenzo Librandi_, Dec 21 2016 %Y A163370 Cf. A000010, A000203, A062401, A062402. %K A163370 nonn,easy %O A163370 1,3 %A A163370 _Jaroslav Krizek_, Jul 25 2009 %E A163370 More terms from _Harvey P. Dale_, Dec 24 2012