%I A055549
%S A055549 3,33,939,75041
%N A055549 Number of normal n X n (-1,0,1)-matrices.
%D A055549 W. H. Press et al., Numerical Recipes, Cambridge, 1986; Chapter 11.
%H A055549 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               NormalMatrix.html">Link to a section of The World of Mathematics.</
               a>
%t A055549 normalQ[a_] := Block[{b=Transpose[a]}, a.b === b.a]; cnt[n_]:= Block[{c=0,
               q=n^2}, Do[If[normalQ@Partition[IntegerDigits[t-1,3,q]-1, n], c++ 
               ],{t,3^q}]; c]; Array[cnt,4]; - Giovanni Resta (g.resta(AT)iit.cnr.it), 
               Apr 03 2006
%Y A055549 Cf. A055547, A055548.
%Y A055549 Sequence in context: A124432 A126466 A002112 this_sequence A086894 A012487 
               A113111
%Y A055549 Adjacent sequences: A055546 A055547 A055548 this_sequence A055550 A055551 
               A055552
%K A055549 nonn,more
%O A055549 1,1
%A A055549 Eric Weisstein (eric(AT)weisstein.com)
%E A055549 a(4) from Giovanni Resta (g.resta(AT)iit.cnr.it), Apr 03 2006