4(3²+1)(3^4+1)……(3^2006+1)
=(3+1)(3²+1)(3^4+1)……(3^2006+1)
=[(3-1)(3+1)(3²+1)(3^4+1)……(3^2006+1)]/2
=[(3²-1)(3²+1)(3^4+1)……(3^2006+1)]/2
=[(3^4-1)(3^4+1)……(3^2006+1)]/2
……
=[(3^2006-1)(3^2006+1)]/2
=(3^4012-1)/2