from math import *
def f(n,xp,xpp):
	return(-10.+19.*xp/3.-2.*xpp)

N = 30
xpp = 2.
xp = 8./3.

for n in range(2,N+1):
	x = f(n,xp,xpp)
	
	xpp = xp
	xp = x
	print n,': ', x