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 A063441 #42 Dec 15 2017 17:35:20
%S A063441 1,-3,-4,0,-6,12,-8,0,0,18,-12,0,-14,24,24,0,-18,0,-20,0,32,36,-24,0,
%T A063441 0,42,0,0,-30,-72,-32,0,48,54,48,0,-38,60,56,0,-42,-96,-44,0,0,72,-48,
%U A063441 0,0,0,72,0,-54,0,72,0,80,90,-60,0,-62,96,0,0,84,-144,-68,0,96,-144,-72,0,-74,114,0,0,96,-168,-80,0,0,126,-84,0,108
%N A063441 a(n) = sigma(n) * mu(n).
%H A063441 Harry J. Smith, <a href="/A063441/b063441.txt">Table of n, a(n) for n=1..2000</a>
%F A063441 a(n) = sum_{d|n} d * mu(n).
%F A063441 a(n) = A000203(n) * A008683(n).
%F A063441 a(n) = A003959(n) * A008683(n) if n is squarefree, 0 otherwise. - _Ralf Stephan_, Mar 26 2004
%F A063441 Multiplicative with a(p^e) = -p-1, if e = 1, 0 otherwise. - _Mitch Harris_, Jun 27 2005, sign flipped by _R. J. Mathar_, May 29 2011
%F A063441 sum(n>0, a(n)/n^s) = product(p prime, 1-p^(-s)-p^(1-s) ). - _Ralf Stephan_, Jul 07 2013
%e A063441 n=6: divisors of 6 are = [1, 2, 3, 6] and 1 * mu(6) + 2 * mu(6) + 3 * mu(6) + 6 * mu(6) = 12.
%t A063441 a[n_] := DivisorSigma[1, n] MoebiusMu[n]; Array[a, 90] (* _Jean-François Alcover_, Dec 05 2015 *)
%o A063441 (PARI) j=[]; for(n=1,200,j=concat(j,sumdiv(n,d,d*moebius(n)))); j
%o A063441 (PARI) a(n)=if(n<1,0,direuler(p=2,n,1-X-p*X)[n]) /* _Ralf Stephan_, Jul 07 2013 */
%o A063441 (PARI) { for (n=1, 2000, write("b063441.txt", n, " ", direuler(p=2, n, 1-X-p*X)[n]) ) } \\ _Harry J. Smith_, Aug 21 2009
%K A063441 easy,sign,mult
%O A063441 1,2
%A A063441 _Jason Earls_, Jul 23 2001