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 A104354 #21 Apr 08 2024 01:38:30 %S A104354 1,1,2,4,16,48,288,576,1728,8640,86400,259200,3110400,21772800, %T A104354 108864000,217728000,3483648000,10450944000,188116992000,940584960000, %U A104354 6584094720000,72425041920000,1593350922240000,4780052766720000,23900263833600000,310703429836800000 %N A104354 Euler's totient of A104350(n). %H A104354 Amiram Eldar, <a href="/A104354/b104354.txt">Table of n, a(n) for n = 1..640</a> %H A104354 Reinhard Zumkeller, <a href="/A104350/a104350.txt">Products of largest prime factors of numbers <= n</a>. %F A104354 a(n) = A000010(A104350(n)). %t A104354 EulerPhi[FoldList[Times, Array[FactorInteger[#][[-1, 1]] &, 30]]] (* _Amiram Eldar_, Apr 08 2024 *) %o A104354 (PARI) gpf(n) = my(f=factor(n)[, 1]); f[#f]; %o A104354 a(n) = eulerphi(prod(i=2, n, gpf(i))); \\ _Michel Marcus_, Nov 12 2023 %Y A104354 Cf. A000010, A048855, A104350. %K A104354 nonn %O A104354 1,3 %A A104354 _Reinhard Zumkeller_, Mar 06 2005 %E A104354 a(1) prepended by _Michel Marcus_, Nov 12 2023