1 2 6 24 120 720 5040 40320 362880 3628800 39916800 479001600 6227020800 87178291200 1307674368000 20922789888000 355687428096000 6402373705728000 121645100408832000 2432902008176640000 51090942171709440000...
1*2=2, 2*3=6, 6*4=24, 24*5=120, 120*6=720, ...
Does this sequence itself flatten out...