ProjectEuler#45 Triangular, pentagonal, and hexagonal

#Triangle, pentagonal, and hexagonal numbers are generated by the following formulae:
#Triangle       Tn=n(n+1)/2      1, 3, 6, 10, 15, ...
#Pentagonal     Pn=n(3n-1)/2     1, 5, 12, 22, 35, ...
#Hexagonal      Hn=n(2n-1)       1, 6, 15, 28, 45, ...

#It can be verified that T285 = P165 = H143 = 40755.

#Find the next triangle number that is also pentagonal and hexagonal.

#Every hexagonal number is a triangular number.
#One can efficiently test whether a positive integer x is an hexagonal number by computing:
#n=(sqrt(8x+1)+1)/4
#If n is an integer, then x is the nth hexagonal number.
#So. 40755 is the H143 number
#Source: http://en.wikipedia.org/wiki/Hexagonal_number
#One can efficiently test whether a positive integer x is an pentagonal number by computing:
#n=(sqrt(24x+1)+1)/6
#If n is an integer, then x is the nth pentagonal number.
#So. 40755 is P165
#Source: http://en.wikipedia.org/wiki/Pentagonal_number

def isPentagonal(n):
    if (((24*n+1)**0.5)+1)%6 == 0:
        return True
    else:
        return False

n = 144
while True:
    hexagon = n*(2*n-1)
    if isPentagonal(hexagon):
        print hexagon
        break
    n += 1