Least prime p such that phi(f(p)) < f(p)/n, where phi is Euler’s totient function and f(p) is the product of the primes up to p.
2, 3, 7, 13, 23, 43, 79, 149, 257, 461, 821, 1451, 2549, 4483, 7879, 13859, 24247, 42683, 75037, 131707, 230773, 405401, 710569, 1246379, 2185021, 3831913, 6720059, 11781551, 20657677, 36221753, 63503639, 111333529, 195199273, 342243401, 600036917
2
The 30th term (20657677) produces a number almost 9000000 digits long!
T. D. Noe, Plot of 35 terms
Wikipedia, Euler’s totient function
(Mma) pr = 1; i = 0; Table[While[i++; pr = pr*Prime[i]/(Prime[i] - 1); pr < n]; Prime[i], {n, 2, 20}]
Cf. A091456 (primorials of the first of these numbers).
nonn,hard
T. D. Noe, Oct 12 2015