for n is odd, the terms follow the pattern
n,n+1,3n+1,5n+1 etc (because you always have that irritating central region)
and for n is even the terms follow the pattern
n, 2n, 4n, 6n, 8n etc.
its a compound series, but thats as far as my memory will get me. i tried to express it in terms of n but i get all fuzzy and irritated. there must be a mathematician or two on this site who see these things when they watch the sky...