This work fine (%i1) s(n):=prod(f(k),k,1,n)$ (%i2) s(3); (%o2) f(1)*f(2)*f(3) (%i3) build_info()$ Maxima version: 5.25.1 Maxima build date: 9:23 9/6/2011 Host type: i686-pc-mingw32 Lisp implementation type: Clozure Common Lisp Lisp implementation version: Version 1.7-r14925M (WindowsX8632) Aleksas D.