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 A085658 #11 Apr 25 2013 03:20:09 %S A085658 1,2,8,64,924,21737,749684,33568376 %N A085658 Number of n X n symmetric positive semi-definite matrices with 2's on the main diagonal and 1's and 0's elsewhere. %C A085658 Of course the total number of symmetric matrices of this type (not necessarily positive semi-definite) is 2^C(n,2). %C A085658 This gives the number of different values of M + M' where M runs through the matrices counted in A038379. - Max Alekseyev, Nov 11 2006 %H A085658 <a href="/index/Mat#binmat">Index entries for sequences related to binary matrices</a> %e A085658 The matrix %e A085658 2 0 0 0 1 %e A085658 0 2 0 1 1 %e A085658 0 0 2 1 1 %e A085658 0 1 1 2 0 %e A085658 1 1 1 0 2 %e A085658 is one of the 100 5 X 5 matrices which are not positive semi-definite. %e A085658 Its eigenvalues are approximately [2., -0.135779205069857, 4.135779205069857, 1.337846553138044, 2.662153446861956] %Y A085658 Cf. A085658, A080858, A083029. %K A085658 nonn,more %O A085658 1,2 %A A085658 _N. J. A. Sloane_, Jul 12 2003 %E A085658 3 more terms from _Max Alekseyev_, Nov 08 2006