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 A068344 #20 Jan 09 2025 02:16:41 %S A068344 0,-1,1,-1,0,1,-1,-1,1,1,-1,-1,0,1,1,-1,-1,-1,1,1,1,-1,-1,-1,0,1,1,1, %T A068344 -1,-1,-1,-1,1,1,1,1,-1,-1,-1,-1,0,1,1,1,1,-1,-1,-1,-1,-1,1,1,1,1,1, %U A068344 -1,-1,-1,-1,-1,0,1,1,1,1,1,-1,-1,-1,-1,-1,-1,1,1,1,1,1,1,-1,-1,-1,-1,-1,-1,0,1,1,1,1,1,1,-1,-1,-1,-1,-1,-1,-1,1,1,1,1 %N A068344 Square array read by antidiagonals of T(n,k) = sign(n-k). %F A068344 a(n-1) = sign(A002260(n) - A004736(n)) or a(n-1) = sign((n-t*(t+1)/2) - ((t*t+3*t+4)/2-n)) where t = floor((-1+sqrt(8*n-7))/2). - _Boris Putievskiy_, Dec 24 2012 %e A068344 The start of the array is: %e A068344 0; %e A068344 -1, 1; %e A068344 -1, 0, 1; %e A068344 -1, -1, 1, 1; %e A068344 -1, -1, 0, 1, 1; %e A068344 ... %e A068344 - _Boris Putievskiy_, Dec 24 2012 %Y A068344 Cf. A049581, A057427, A057428, A002260, A004736. As a straight sequence, a(n)=0 when n is in A046092. A023532 seen as a triangle is half this square. %K A068344 easy,sign,tabl %O A068344 0,1 %A A068344 _Henry Bottomley_, Mar 06 2002