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 A087987 #34 Nov 10 2024 05:19:23
%S A087987 0,-1,-3,-1,-1,16,-25,278,3516,-5012,-30431,-234676,-4247453,-6271957,
%T A087987 177533446,-416214476
%N A087987 a(n) is the Mertens function value at the n-th primorial number.
%H A087987 Marc Deléglise and Joël Rivat, <a href="http://projecteuclid.org/euclid.em/1047565447">Computing the summation of the Mobius function</a>, Experiment. Math. 5:4 (1996), pp. 291-295.
%F A087987 a(n) = A002321(A002110(n)).
%e A087987 n = 3: 3rd primorial number = 30. A002321(30) = -3.
%t A087987 q[x_] := Apply[Times, Table[Prime[i], {i, 1, x}]] s=0; i=1; Do[While[i<=q[n], s=s+MoebiusMu[i]; i++ ]; Print[s], {n, 0, 8}]//Timing
%o A087987 (PARI) p=1; s=1; for(n=1,10,pr=p; p*=prime(n); s+=sum(k=pr+1, p, moebius(k)); print1(s",")) \\ Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 21 2007
%o A087987 (Perl) use ntheory ":all"; say mertens(pn_primorial($_)) for 1..12; # _Dana Jacobsen_, May 22 2015
%Y A087987 Cf. A002110, A002321, A008683, A084237.
%K A087987 more,sign
%O A087987 1,3
%A A087987 _Labos Elemer_, Oct 02 2003
%E A087987 One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 21 2007
%E A087987 a(10)-a(11) from _Donovan Johnson_, Jun 21 2012
%E A087987 a(12)-a(13) from _Rikard Nordgren_, Nov 11 2012
%E A087987 a(14) from _Chai Wah Wu_, Apr 24 2021
%E A087987 a(15)-a(16) from _Henri Lifchitz_, Nov 10 2024