10! = 3628800, 20! = 2432902008176640000
2^10 = 1024, 2^-3 = 0.125
primes in [1, 50]: 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 
by pointer:   oldest 1980, newest 2009
by reference: oldest 1980, newest 2009
