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 A047885 #9 Mar 07 2020 00:47:37 %S A047885 0,0,0,0,1,0,0,1,1,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,-1,0,0,0,0,1,0,0,0,0, %T A047885 1,0,0,0,0,-1,0,-1,0,0,0,0,0,-1,-1,-1,-1,-1,-1,0,0,0,0,-1,-2,-1,-2,-1, %U A047885 -2,-1,0,0 %N A047885 Array a(m,n) = pi(m+n) - pi(m) - pi(n) read by antidiagonals, where pi() = A000720 (m,n >= 0). %C A047885 A212210-A212213 are the preferred versions of this array. %e A047885 Beginning of array is %e A047885 0 0 0 0 0 0 0 0 ... %e A047885 0 1 1 0 1 0 1 0 ... %e A047885 0 1 0 0 0 0 -1 ... %e A047885 0 0 0 -1 0 -1 -1 ... %e A047885 ... %Y A047885 Cf. A047886, A212210-A212213, A000720. %K A047885 sign,tabl,easy %O A047885 0,59 %A A047885 _N. J. A. Sloane_