#!/usr/bin/env python
# coding: utf-8

# Evaluating the formula from:
# 
# http://www.johndcook.com/blog/2015/08/20/when-is-a-triangle-a-square/

# In[1]:


from sympy import var, sqrt, init_printing
init_printing()


# In[2]:


var("n")


# In[3]:


e = ((17+12*sqrt(2))**n + (17-12*sqrt(2))**n - 2 ) / 32
e


# In[4]:


for n_ in range(1, 20):
    print n_, e.subs(n, n_).expand()