Project Euler #44

euler44.py

from math import sqrt
from itertools import count
from itertools import islice

def f(n): return n * (3 * n - 1) / 2                  # nth pentagonal
def p(n): return not ((sqrt(24 * n + 1) + 1) / 6) % 1 # is  pentagonal

print islice((abs(f(i) - f(j))
                for i in count(2)
                    for j in xrange(i - 1, 1, -1)
                        if p(f(i) + f(j))
                            and p(abs(f(i) - f(j)))), 1).next()