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 A088668 #26 Jul 13 2025 11:08:49 %S A088668 1,6,112,7680,2031616,2113929216,8727373545472,143552238122434560, %T A088668 9426286221665580875776,2473462226931531291448836096, %U A088668 2594880778667185584863751461404672,10886377285478460999082179823696022077440,182665403921164334152319068371262729095485587456 %N A088668 Number of n X n matrices over GF(2) with characteristic polynomial x^(n-1) * (x-1). %H A088668 Irving Reiner, <a href="http://doi.org/10.1215/ijm/1255629830">On the number of matrices with given characteristic polynomial</a>, Illinois Journal of Mathematics, Vol. 5, No. 2 (1961), pp. 324-329. %F A088668 a(n) = (q/(q-1))*(q^(n^2-n)-q^(-2*n+n^2)) where q = 2. %t A088668 a[n_] := 2*(2^(n^2-n) - 2^(n^2-2*n)); Array[a, 10] (* _Amiram Eldar_, Jul 13 2025 *) %o A088668 (PARI) a(n)=(2^n-1)<<(n^2-2*n+1) \\ _Charles R Greathouse IV_, Oct 04 2013 %Y A088668 Cf. A088671, A088852, A088853. %K A088668 nonn,easy %O A088668 1,2 %A A088668 Yuval Dekel (dekelyuval(AT)hotmail.com) and _W. Edwin Clark_, Nov 29 2003 %E A088668 More terms from _Joerg Arndt_, Oct 04 2013