>>8
First thing I did was plop it into Wolfram Alpha to see if it could guess the sequence. The difference table it gives shows that this is not a polynomial(or if it is, it's a 10th degree convoluted one that doesn't make any sense).
Second thing was try tho OEIS, and it didn't show up there.
Strictly speaking, it's nonsense to speak of finding the 1000th member of a finite sequence. You could add whatever terms you wanted and still get a sequence, even if they weren't described by a formula.