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 A266462 #38 May 20 2025 08:55:40
%S A266462 1,1,2,5,10,20,41,82,166,334,667,1336,2682,5360,10724,21467,42936,
%T A266462 85876,171786,343574,687184,1374427,2748852,5497766,10995706,21991402,
%U A266462 43982908,87966150,175932383,351864964,703730584,1407461288,2814923196,5629847656,11259695532
%N A266462 The number of conjugacy classes of invertible n X n matrices over GF(2) which are squares of other such matrices.
%C A266462 It follows from the form of the generating function that a(n) is asymptotic to alpha*2^n where alpha = Product_{m>=1} (1-(1/16)^m)*(1-2*(1/4)^m)/((1-2*(1/16)^m)*(1-(1/4)^m)). [corrected by _Jason Yuen_, May 19 2025]
%H A266462 N. J. A. Sloane, <a href="/A266462/b266462.txt">Table of n, a(n) for n = 0..60</a> [Based on the table in Miller (2016)]
%H A266462 Victor S. Miller, <a href="http://arxiv.org/abs/1606.09299">Counting Matrices that are Squares</a>, arXiv:1606.09299 [math.GR], 2016.
%H A266462 <a href="/index/Mat#binmat">Index entries for matrices, binary, which are squares</a>
%F A266462 G.f.: Product_{n>=1} (1-2*x^(2*n))*(1-x^(2*n))/((1-2*x^n)*(1-2*x^(4*n))*(1+x^(2*n-1))).
%t A266462 terms = 35; CoefficientList[Product[(1-2x^(2n))(1-x^(2n))/((1-2x^n) (1-2x^(4n))(1+x^(2n-1))), {n, 1, terms}] + O[x]^terms, x] (* _Jean-François Alcover_, Aug 06 2018 *)
%Y A266462 Cf. A006950.
%K A266462 nonn
%O A266462 0,3
%A A266462 _Victor S. Miller_, Dec 29 2015
%E A266462 More terms from _Alois P. Heinz_, Dec 29 2015