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 A060239 #9 Mar 14 2020 11:27:23 %S A060239 1,-1,4,-8,128,512,-18432,73728,-884736,-14155776,1415577600, %T A060239 11324620800,-1630745395200,-58706834227200,-3757237390540800, %U A060239 30057899124326400,-7694822175827558400,-92337866109930700800 %N A060239 a(n) = determinant(P*Q)/n! where P, Q are n X n matrices with P[i,j]=lcm(i,j), Q[i,j]=gcd(i,j). %H A060239 Enrique Pérez Herrero, <a href="/A060239/b060239.txt">Table of n, a(n) for n = 1..100</a> %F A060239 a(n) = A001088(n)*A060238(n)/n!. %o A060239 (Sage) %o A060239 def A060239(n): %o A060239 P = Matrix(lambda i,j: lcm(i+1,j+1), nrows=n) %o A060239 Q = Matrix(lambda i,j: gcd(i+1,j+1), nrows=n) %o A060239 return (P*Q).det()/factorial(n) # _D. S. McNeil_, Jan 16 2011 %Y A060239 Cf. A001088, A060238. %K A060239 sign %O A060239 1,3 %A A060239 MCKAY john (mckay(AT)cs.concordia.ca), Mar 21 2001