For just printing the values of Euler's phi function of integers
n between 1 and 20 write:

	for(n=1, 20, print(n, "   ", eulerphi(n)))




For printing the values of Euler's phi function of primes
n between 1 and 20 write:

	forprime(n=1, 20, print(n, "   ", eulerphi(n)))




For printing those n's between 1 and 20 for which phi(n) = n/2 write

	for(n=1, 20, if(eulerphi(n) == n/2, print(n, "   ", eulerphi(n)),))




For checking how the ratio phi(n)/n behaves for n between 1 and 20 write

	for(n=1, 20, print(eulerphi(n)/n*1.0))



For checking how small phi(n)/n can get for n between 1 and 20 write the following
(you can replace 20 by 10^7 without making PARI sweat)

	a = 1; for(n=1, 20, if(eulerphi(n)/n>a, , a = eulerphi(n)/n));print(a*1.0)