A067562 Odd values of k such that phi(k)! divides phi(k!) where phi(k) = A000010(k).

1, 3, 15, 63, 75, 105, 165, 195, 231, 255, 285, 315, 495, 525, 585, 735, 825, 945, 975, 1155, 1275, 1365, 1485, 1575, 1755, 1785, 1815, 1995, 2145, 2205, 2415, 2475, 2535, 2625, 2805, 2835, 2925, 3003, 3045, 3135, 3255, 3315, 3465, 3675, 3705, 3795, 3885, 3927

Offset: 1

Author

Benoit Cloitre, Jan 29 2002; corrected Jun 03 2003

Keywords

• nonn

Comments

a(n) == 0 (mod 3) for any n > 1.

k cannot be divisible by 5 for k = 1, 3, 63, 231, 3003, 3927, 4389, 4641, 5187, 5313, 9009, 11781, 13167, 13923, 15561, 15939, 21021, 27027, 27489, 30723, ... - Jinyuan Wang, Apr 05 2020

Crossrefs

Cf. A000010, A048855.

Programs

PARI

is(k) = (k%6==3 && eulerphi(k!)%eulerphi(k)!==0) || k==1; \\ Jinyuan Wang, Apr 05 2020

Extensions

More terms from Jinyuan Wang, Apr 05 2020