I am trying to solve numerically Helium atom problem (spectrum of two electrons with interaction with nucleus and electronic repulsion).. I have excluded the kinetic term of nucleus and put the origin at the nucleus. I have constructed two body states with hydrogen atom basis (minimal), 1s, 2s, 2p1, 2p0, 2p-1. . Now, I constructed the matrix elements of the electronic hamiltonian of the in the two body states.To calculate the matrix elements of the two body states, I need to integrate the two electron part of the Hamiltonian.How do I do that numerically ? Can someone suggest and algorithm in C or python to do it or some references to understand that better? Is it better to do in Mathematica ?