These are just the known values. There is no proof that this sequence is correct (in the usual sense that there are no other terms below the last term shown). - N. J. A. Sloane, Nov 07 2006

Factorization: 2^(n-1)*M(n)*3*5^2*13*31*139*277*3877*11*19 where M(n) is Mersenne Prime, n=3 or 5<n.