Could someone point me in the correct direction regarding evaluations of such sums:

Terje
Hi,
for reproducing that formula, just type:
el(η,m):sum(el(K,i)*(1+2*sum(el(H,i,j)*el(K,j),j,1,i-1)+sum(sum(el(H,j,k)*el(H,i,k)*el(K,j)*el(K,k)*(j≠i)*(k≠i),k,1,n),j,1,n)),i,1,n)
to obtain:

Regards,
Oscar.