A068582 Let phi_m(x) = phi(phi(...(phi(x))...)) m times; sequence gives values of k such that phi_5(k) = tau(k).

1, 41, 47, 53, 59, 61, 67, 71, 73, 79, 85, 109, 115, 119, 123, 125, 127, 141, 143, 145, 155, 159, 161, 163, 166, 177, 178, 183, 185, 194, 201, 202, 203, 206, 209, 213, 214, 215, 217, 219, 226, 237, 247, 255, 259, 262, 278, 298, 301, 302, 314, 327, 328, 343

Offset: 1

Author

Benoit Cloitre, Mar 26 2002

Keywords

• nonn
• easy
• fini
• full

Comments

Last term is a(340) = 24570.

Numbers k such that A049107(k) = A000005(k).

Links

• Jinyuan Wang, Table of n, a(n) for n = 1..340

Crossrefs

Cf. A000005, A000010, A049107, A068579, A068580, A068581.

Programs

Mathematica

Select[Range[343], Nest[EulerPhi, #, 5] === DivisorSigma[0, #] &] (* Amiram Eldar, Jun 12 2022 *)