symbolic sum of gaussian functions

Hello

I have some data which can be represented as the sum of several (>8) gaussian functions.

Positions and widths are fixed and I would like to fit the data and determine only the amplitudes.

I could write a custom fitting function but the gaussians are of the order of 30 ( the actual number can change for different data set) and the procedute would be awful.

Any whay to construct such sum symbolically obtaining someting like

a[1]*exp(-((x-b[1])/c[1])^2)+....a[m]*exp(-((x-b[m])/c[m])^2)

where a[i] are the parameters to fit and b[i] and c[i] are known?

Thanks

Renzo