Hi, Many thanks Jacque i did some research on the seq command. I have changed the code from: for t1 from 2 to 10 do for i from 0 to (u+t-t1) do d[i,t1] := evalf(sum(d[i+1-j,t1-1]*g[j],j=0..i+1)); end do: end do: to d1 := proc(a,b,c) d[a,b] := add(d[a+1-j,b-1]*g[j],j=0..a+1); end: [seq(seq(d1(i,t1),i=0..u+t-t1),t1=2..2)]: This has speeded things up. I think that having to write values to an array is causing the procedure to slow down. Anyone have any suggestions? Thanks in advance Matthew