kill(all)$

fpprintprec:4$

load(solve_rec)$

van=facebook.com/LearningCalculus$

f(n,a):=''(rhs(solve_rec(x[n+1]=x[n]/((2*(2*n+1)*x[n]+1)),x[n],x[1]=a)));

f(1,2/3); f(2,2/3); f(10,2/3); f(100,2/3);

sum(f(n,a),n,1,3);

f(20/3,2/3);

float(%);

sum(f(n,2/3),n,1,100);

sum(f(n,-1/50),n,1,100);

float(%);

set_plot_option(['plot_format, 'gnuplot_pipes])$

expr_1: n$
expr_2: a$
expr_3: f(n,a)$
plot3d (
        [expr_1, expr_2, expr_3],
        [n, -4, 4],[a, -4, 4],
        ['grid, 200, 200]);