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 A094813 #4 Nov 20 2017 11:33:57 %S A094813 1,13,10,33,84,338,84,360,1200,10020,42976,10020,12003600,42795, %T A094813 145485,1206772,4848581,21059938,4848585,1206796,145473,42807,3600 %N A094813 a(n) = number of (0,1) matrices of size n X n whose determinants are k, where -L <= k <= +L and L = A003432(n). %H A094813 J. Brenner, <a href="http://www.jstor.org/stable/2317092">The Hadamard maximum determinant problem</a>, Amer. Math. Monthly, 79 (1972), 626-630. %H A094813 J. Williamson, <a href="http://www.jstor.org/stable/2306240">Determinants whose elements are 0 and 1</a>, Amer. Math. Monthly 53 (1946), 427-434. Math. Rev. 8,128g. %e A094813 n = 2 : det([a b];[c d]) is (ad - bc) [16 possible matrices] %e A094813 0 if ((a OR d) = zero) AND ((b OR c) = zero) %e A094813 OR ((a AND d) = one) AND ((b AND D) = one) [10 possible matrices] %e A094813 +1 if ((a AND d) = one) AND ((b OR c) = zero) [ 3 possible matrices] %e A094813 -1 if ((a OR d) = zero) AND ((b AND c) = one) [ 3 possible matrices] %Y A094813 Cf. A003432, A003433. %K A094813 hard,nonn %O A094813 1,2 %A A094813 Patricia J. Egan (capdevcom(AT)lycos.com), Jun 11 2004