OFFSET
1,1
COMMENTS
Numbers k such that phi(k)/k = m
( Family of sequences for successive n odd primes )
m=2/3 numbers with exactly 1 distinct prime divisor {3} see A000244;
m=8/15 numbers with exactly 2 distinct prime divisors {3,5} see A033849;
m=16/35 numbers with exactly 3 distinct prime divisors {3,5,7} see A147576;
m=32/77 numbers with exactly 4 distinct prime divisors {3,5,7,11} see A147577;
m=384/1001 numbers with exactly 5 distinct prime divisors {3,5,7,11,13} see A147578;
m=6144/17017 numbers with exactly 6 distinct prime divisors {3,5,7,11,13,17} see A147579;
m=3072/323323 numbers with exactly 7 distinct prime divisors {3,5,7,11,13,17,19} see A147580;
m=110592/323323 numbers with exactly 8 distinct prime divisors {3,5,7,11,13,17,19,23} see A147581.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
Sum_{n>=1} 1/a(n) = 1/5760. - Amiram Eldar, Dec 22 2020
MATHEMATICA
a = {}; Do[If[EulerPhi[x]/x == 384/1001, AppendTo[a, x]], {x, 1, 1000000}]; a
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Nov 07 2008
EXTENSIONS
More terms from Amiram Eldar, Mar 11 2020
STATUS
approved