%I
%S 0,2,120,18624,9876480,20135116800,163839423283200,
%T 5348052945894113280,699612285096273924587520,
%U 366440137172271078986848665600,768105432116827516249785005978419200,6441762292785726797799215491828242028953600
%N Number of n X n matrices over GF(2) that can be used as a kernel to construct a polar code. That is, the number of matrices for which channel polarization occurs.
%C An n X n matrix is polarizing if it is nonsingular, and there is no permutation of its columns that results in an uppertriangular matrix.
%D S. B. Korada, E. Sasoglu and R. Urbanke, Polar Codes: Characterization of Exponent, Bounds, and Constructions, IEEE Transactions on Information Theory, 56 (2010), 62536264
%F a(n) = Product_{i=0..n1} (2^n  2^i)  n! * 2^(n*(n  1)/2).
%t a[n_]:=Product[2^n  2^i, {i, 0, n  1}]  n!*2^(n*(n  1)/2); Array[a,10]
%K nonn,easy
%O 1,2
%A _Ido Tal_, Mar 14 2011
