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 A187880 #9 Dec 16 2016 03:05:41
%S A187880 0,2,120,18624,9876480,20135116800,163839423283200,
%T A187880 5348052945894113280,699612285096273924587520,
%U A187880 366440137172271078986848665600,768105432116827516249785005978419200,6441762292785726797799215491828242028953600
%N A187880 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 A187880 An n X n matrix is polarizing if it is non-singular, and there is no permutation of its columns that results in an upper-triangular matrix.
%D A187880 S. B. Korada, E. Sasoglu and R. Urbanke, Polar Codes: Characterization of Exponent, Bounds, and Constructions, IEEE Transactions on Information Theory, 56 (2010), 6253-6264
%F A187880 a(n) = Product_{i=0..n-1} (2^n - 2^i) - n! * 2^(n*(n - 1)/2).
%t A187880 a[n_]:=Product[2^n - 2^i, {i, 0, n - 1}] - n!*2^(n*(n - 1)/2); Array[a,10]
%K A187880 nonn,easy
%O A187880 1,2
%A A187880 _Ido Tal_, Mar 14 2011