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 A089035 #17 Jul 24 2025 08:38:03
%S A089035 1,4,56,4096,666624,1194590208,3343877406720,72057594037927936,
%T A089035 3701652434038082764800,1021880992906173430024372224,
%U A089035 750836199529096452135514747699200,7415506491123333639280491668337906941952,52777360037873674206622083843242895013104844800
%N A089035 Number of n X n matrices over GF(2) with characteristic polynomial x^n - 1.
%H A089035 I. Reiner, <a href="https://projecteuclid.org/euclid.ijm/1255629830">On the number of matrices with given characteristic polynomial</a>, Illinois J. Math. 5 1961 324-329.
%o A089035 (PARI) \\ see Reiner reference.
%o A089035 F(u,r)={prod(i=1, r, (1-u^(-i)))}
%o A089035 a(n, q=2)={my(D=ffgen(q)); my(f=factor(D^0*(x^n-1))); q^(n^2-n)*F(q,n)/prod(i=1, #f~, F(q^poldegree(f[i,1]), f[i,2]))} \\ _Andrew Howroyd_, Jul 08 2018
%Y A089035 Cf. A088654, A089036, A089037, A335804.
%K A089035 nonn
%O A089035 1,2
%A A089035 Yuval Dekel (dekelyuval(AT)hotmail.com) and _W. Edwin Clark_, Nov 29 2003
%E A089035 Offset corrected and a(11)-a(13) from _Andrew Howroyd_, Jul 08 2018