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 A189100 #6 Mar 31 2012 10:28:21 %S A189100 0,2,30,66,1830,645,33180,198870,228270,64785,7960260,9738960, %T A189100 1663226565,7232635410,857066210,1057466410,307311194190,767464487790, %U A189100 278292627277665,306517823106495,35302033071305,147385363695570,78207294248313230,198777858520921680 %N A189100 a(n) = lcm(n!,n!')/gcd(n!,n!'), where n!' is the arithmetic derivative of n! (A068311). %C A189100 Least common multiple of n! and its arithmetic derivative divided by greatest common divisor of n! and its arithmetic derivative. %H A189100 Nathaniel Johnston, <a href="/A189100/b189100.txt">Table of n, a(n) for n = 1..200</a> %F A189100 a(n) = lcm(n!,n!')/gcd(n!,n!') = A086130(n!)/A085731(n!) = lcm(A000142(n),A068311(n))/gcd(A000142(n),A068311(n)) %e A189100 n = 5: 5! = 120, 120' = 244, gcd(120,244) = 4, lcm(120,244) = 7320, 7320/4 = 1830 -> a(5) = 1830. %Y A189100 A068311, A083346, A083346, A085731, A086130 %K A189100 nonn %O A189100 1,2 %A A189100 _Giorgio Balzarotti_, Apr 16 2011