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 A131483 #7 Oct 11 2017 18:13:11
%S A131483 1,0,-1,0,-1,-1,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,0,0,1,1,1,1,1,0,0,1,1,1,
%T A131483 1,1,1,0,0,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,1,1,0,
%U A131483 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,1,1,1,1
%N A131483 Meissel_Lehmer recursion: a(n,m) = a(n,m-1)-a(Floor[n/Prime[m]],m-1).
%H A131483 J. C. Lagarias, V. S. Miller and A. M. Odlyzko, <a href="https://doi.org/10.1090/S0025-5718-1985-0777285-5">Computing pi(x): The Meissel-Lehmer method</a>, Math. Comp., 44 (1985), pp. 537-560.
%F A131483 a(1,1) = 1; a(n,m) = a(n,m-1)-a(Floor[n/Prime[m]],m-1);
%e A131483 {1},
%e A131483 {0, -1},
%e A131483 {0, -1, -1},
%e A131483 {0, 0, 0, 0},
%e A131483 {0, 0, 0, 0, 0},
%e A131483 {0, 0, 1, 1, 1, 1},
%e A131483 {0, 0, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
%e A131483 {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
%e A131483 {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
%e A131483 {0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
%e A131483 {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
%Y A131483 Cf. A000720, A006880, A007053, A075986, A059305.
%K A131483 tabl,sign
%O A131483 1,1
%A A131483 _Roger L. Bagula_, Oct 01 2007