sum(1/n,n,1,4);

lsum(1/n, n, [1, 3, 5]);

product(1/n,n,1,4);

sum(1/n,n,1,inf);

product (a + 2*n, n, 1, 4);

product (a + 2*n, n, 1, 4)+product (a + 2*n, n, 1, 4);

product (k, k, 1, n), simpproduct;