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 A174856 #11 Mar 23 2024 17:31:28
%S A174856 1,1,1,1,1,1,0,0,0,1,1,1,1,0,1,1,0,0,0,0,1,1,1,0,1,0,0,1,1,0,1,0,0,0,
%T A174856 0,1,0,1,0,0,1,0,0,0,1,1,0,0,0,0,0,0,0,0,1,1,1,1,1,0,1,0,0,0,0,1,1,0,
%U A174856 0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,1,0,0,0,0,0,1,1,0,1,0,1,0,0,0,0,0,0,0,0,1
%N A174856 Square array read by antidiagonals up. Redheffer type matrix. T(1,1)=1 and T(n,1) = A049240.
%C A174856 The first column is equal to 0 when n is a square greater than 1. The rest of the array is equal to A143104. The determinant of this array is A002819.
%e A174856 The array begins:
%e A174856 1,1,1,1,1,1,1,1,1,1
%e A174856 1,1,0,0,0,0,0,0,0,0
%e A174856 1,0,1,0,0,0,0,0,0,0
%e A174856 0,1,0,1,0,0,0,0,0,0
%e A174856 1,0,0,0,1,0,0,0,0,0
%e A174856 1,1,1,0,0,1,0,0,0,0
%e A174856 1,0,0,0,0,0,1,0,0,0
%e A174856 1,1,0,1,0,0,0,1,0,0
%e A174856 0,0,1,0,0,0,0,0,1,0
%e A174856 1,1,0,0,1,0,0,0,0,1
%t A174856 t[1, 1] = 1; t[n_, 1] := Boole[!IntegerQ[Sqrt[n]]]; t[n_, k_] := Boole[n == 1 || Mod[n, k] == 0]; Table[t[n - k + 1, k], {n, 1, 14}, {k, 1, n}] // Flatten (* _Jean-François Alcover_, Dec 05 2013 *)
%Y A174856 Cf. A143104, A002819, A174854, A174852.
%K A174856 nonn,tabl
%O A174856 1,1
%A A174856 _Mats Granvik_, Mar 31 2010