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 A144778 #2 Mar 31 2012 19:53:15 %S A144778 1,-1,-1,-1,1,1,0,0,0,-1,-1,-1,1,0,1,1,0,0,0,0,-1,-1,-1,0,1,0,0,1,0,0, %T A144778 -1,0,0,0,0,-1,0,0,0,0,1,0,0,0,1,1,0,0,0,0,0,0,0,0,-1,-1,-1,-1,-1,0,1, %U A144778 0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,-1,-1,1,0,0,0,0,1,0,0,0,0,0,1,1,0,0,0,-1 %N A144778 Square array T(n,k) read by antidiagonals upwards. Mobius function interleaved with k-1 zeros in each column. Every second value in the first row is either 1 or -1. Redheffer type matrix. %C A144778 The determinant of this matrix appears to be A059841. %F A144778 T(n,k) = if(n==1 then if(k mod 2==0 then -1 else 1) else if(n mod k == 0 then A008683(n/k) else 0)). %e A144778 Table begins: %e A144778 .1.-1..1.-1..1.-1..1 %e A144778 -1..1..0..0..0..0..0 %e A144778 -1..0..1..0..0..0..0 %e A144778 .0.-1..0..1..0..0..0 %e A144778 -1..0..0..0..1..0..0 %e A144778 .1.-1.-1..0..0..1..0 %e A144778 -1..0..0..0..0..0..1 %Y A144778 Cf. A008683, A059841, A143142. %K A144778 sign,tabl %O A144778 1,1 %A A144778 _Mats Granvik_, Sep 21 2008