A049225 Values of totient function applied to squarefree numbers; or numbers of form Product (p_i-1) where p_i are distinct primes.

1, 2, 4, 6, 8, 10, 12, 16, 18, 20, 22, 24, 28, 30, 32, 36, 40, 42, 44, 46, 48, 52, 56, 58, 60, 64, 66, 70, 72, 78, 80, 82, 84, 88, 92, 96, 100, 102, 104, 106, 108, 112, 116, 120, 126, 128, 130, 132, 136, 138, 140, 144, 148, 150, 156, 160, 162, 164, 166, 168, 172, 176

Offset

1,2

Comments

Numbers m such that m = phi(k) and |mu(k)| = 1.

Links

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

Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).

Example

8, 120, 48 are terms as totients of the squarefree numbers 15, 143, 210.
54, 110 are not terms since there are no squarefree numbers k such that phi(k) = 54, 110.

Prog

(PARI) isok(n) = {my(v = invphi(n)); (#v) && (#select(x->issquarefree(x), v)); } \\ Michel Marcus, Feb 25 2019

Crossrefs

Terms of A049200 after ordering and omitting multiple occurrences.

Cf. A000010, A005117, A008683, A013929, A002174, A002202, A049200.

Sequence in context: A340521 A002174 A002202 * A378508 A351910 A371177

Adjacent sequences: A049222 A049223 A049224 * A049226 A049227 A049228

Keyword

nonn

Author

Labos Elemer

Status

approved