A085346 Least number x so that number of primes between sigma(x) and phi(x) equals n.

3, 2, 4, 6, 10, 14, 12, 26, 18, 34, 28, 32, 24, 62, 44, 30, 123, 40, 36, 64, 56, 106, 54, 48, 70, 66, 146, 105, 88, 78, 80, 135, 60, 178, 72, 102, 202, 112, 84, 164, 114, 90, 96, 154, 695, 231, 138, 108, 184, 1141, 176, 140, 126, 244, 132, 160, 326, 232, 186, 208, 120

Offset: 1

Author

Labos Elemer, Jul 10 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000720, A000010, A000203, A070803, A070804, A085341-A085347.

Programs

PARI

s(n) = my(f = factor(n)); primepi(sigma(f)) - primepi(eulerphi(f));
list(len) = {my(v = vector(len), k = 1, c = 0, i); while(c < len, i = s(k); if(i > 0 && i <= len && v[i] == 0, c++; v[i] = k); k++); v;} \\ Amiram Eldar, Dec 20 2024

Formula

a(n) = Min{x; A085343(x) = n}.