N=2:6;
a=zeros(1,length(N));
for m=2:6

k=2^m;
N1(m-1)=k;
k1=(2^m-2);
b=1;
while (k>1)
b=b*k*(k-1);
k=k-2;
end
b1=1;
while (k1>1)
if  k1>0
b1=b1*k1*(k1-1);
k1=k1-2;
end
end
a(m-1)=b/(2*b1);

end

a1=log2(a);
for k=1:5
    a1(k)=a1(k)/(N1(k));
end
hold on
plot(N,a1,'-s ');
hold off