# Question:Problem with sum

## Question:Problem with sum

Maple 2024

I'm new to Mapple 2024, and probably miss something.
lie, e[i] i=1..4, and G are previously defined objects. Then whe I define:

cf:=(k,l,m,t,x,y,z)->seq(lie(p,e[k](t,x,y,z),e[l](t,x,y,z))*G(t,x,y,z)[p,m],p=1..4);
cf(2,4,2,t,x,y,z);

I get:

0, 0, 0, -6*(-6*z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^2*x - 6*z^4*(1 - z)^3*(-x^2 + 1)^2*(-y^2 + 1)^3*x*(-3*z^2*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3 - 7*z^3*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3 - 2*z^3*(7*z - 4)*(z - 1)*(y^2 - 1)^3*(x^2 - 1)^3) - (1 - z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3)*(-24*z^3*(1 - z)^3*(-x^2 + 1)^2*(-y^2 + 1)^3*x + 18*z^4*(1 - z)^2*(-x^2 + 1)^2*(-y^2 + 1)^3*x))*z^4*(1 - z)^3*(-x^2 + 1)^2*(-y^2 + 1)^3*x*(1 - z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3)

The 4th item eval as:
cf(2, 4, 2, t, x, y, z)[4] = -36*z^10*x^2*(x^2 - 1)^7*(7*z^2 - 8*z + 4)*(z - 1)^7*(y^2 - 1)^9*(-1 + z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3)

But when I define another function by just changing the seq operator with a sum operator:

cf2:=(k,l,m,t,x,y,z)->sum(lie(p,e[k](t,x,y,z),e[l](t,x,y,z))*G(t,x,y,z)[p,m],p=1..4);
cf2(2,4,2,t,x,y,z);

I get 0.

What do I miss ?

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