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 A161780 #7 Feb 18 2024 01:27:16 %S A161780 1,-2,1,-2,1,1,1,0,0,1,-2,-2,1,0,1,4,0,0,0,0,1,-2,-2,0,1,0,0,1,0,0,-2, %T A161780 0,0,0,0,1,1,1,0,0,1,0,0,0,1,4,0,0,0,0,0,0,0,0,1,-2,-2,-2,-2,0,1,0,0, %U A161780 0,0,1,-2,0,0,0,0,0,0,0,0,0,0,1,-2,4,0,0,0,0,1,0,0,0,0,0,1,4,0,1 %N A161780 Square array read by antidiagonals up. Redheffer type matrix. A007427 interleaved with k-1 zeros in the columns. %C A161780 The determinant of this matrix is A006218. %e A161780 Table begins: %e A161780 ..1..1..1..1..1..1..1..1 %e A161780 .-2..1..0..0..0..0..0..0 %e A161780 .-2..0..1..0..0..0..0..0 %e A161780 ..1.-2..0..1..0..0..0..0 %e A161780 .-2..0..0..0..1..0..0..0 %e A161780 ..4.-2.-2..0..0..1..0..0 %e A161780 .-2..0..0..0..0..0..1..0 %e A161780 ..0..1..0.-2..0..0..0..1 %o A161780 (Excel) =if(row()=1;1;if(mod(row();column())=0;1*lookup(row()/column();A000027;A007427);0)) %Y A161780 Cf. A007427, A006218, A002321. %K A161780 sign,tabl %O A161780 1,2 %A A161780 _Mats Granvik_, Jun 19 2009