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 A070890 #10 Mar 17 2015 02:13:12
%S A070890 -1,2,-1,19,-1,304,-81988,410857,-249979,4165258,-65721449,2562470143,
%T A070890 -5468849774,184344882947,-137190436674212,10026981687881,
%U A070890 -12611493192339623,519973962150962777,-8549627883788520181,1874648830674470878723,-200643437220052588790575,877316785444551755504875
%N A070890 Numerator of Sum_{k=1..n} mu(k)/k when it changes sign.
%e A070890 a(1)= -1 because numerator first sign change is 1-1/2-1/3-1/5= > (-1)/30 <0.
%e A070890 a(2)= 2 because next sign change is -1/30+1/6 = 2/15, reverts to positive.
%o A070890 (PARI) t = 0; v = []; for( n = 1, 120, t1 = t; t = t + moebius(n) / n; if( t * t1 < 0, v = concat( v, numerator( t)), )); v
%Y A070890 Cf. A070891, A070888, A070889.
%K A070890 frac,sign,easy
%O A070890 1,2
%A A070890 _Donald S. McDonald_, May 17 2002