load('pfaff)$
pfaffian(1,[a]);
pfaffian(2,[a,b,c]);
pfaffian(3,[a,b,c,d,e,f]);
pfaffian(4,[a,b,c,d,e,f,g,h,j,k]);
pfaffian(5,[a,b,c,d,e,f,g,h,i,j,k,l,m,n,o]);
pfaffian(7,[a,b,c,d,e,f,g,
            h,i,j,k,l,m,n,aa,ba,ca,da,ea,fa,ga,ha,ia,ja,ka,la,ma,na]);