A147579 - OEIS

%I #11 Dec 22 2020 02:14:14

%S 255255,765765,1276275,1786785,2297295,2807805,3318315,3828825,

%T 4339335,5360355,6381375,6891885,8423415,8933925,9954945,11486475,

%U 12507495,13018005,14039025,16081065,16591575,19144125,19654635,20675655,21696675,23228205,25270245,26801775

%N Numbers with exactly 6 distinct odd prime divisors {3,5,7,11,13,17}.

%C Numbers k such that phi(k)/k = m

%C ( Family of sequences for successive n odd primes )

%C m=2/3 numbers with exactly 1 distinct prime divisor {3} see A000244

%C m=8/15 numbers with exactly 2 distinct prime divisors {3,5} see A033849

%C m=16/35 numbers with exactly 3 distinct prime divisors {3,5,7} see A147576

%C m=32/77 numbers with exactly 4 distinct prime divisors {3,5,7,11} see A147577

%C m=384/1001 numbers with exactly 5 distinct prime divisors {3,5,7,11,13} see A147578

%C m=6144/17017 numbers with exactly 6 distinct prime divisors {3,5,7,11,13,17} see A147579

%C m=3072/323323 numbers with exactly 7 distinct prime divisors {3,5,7,11,13,17,19} see A147580

%C m=110592/323323 numbers with exactly 8 distinct prime divisors {3,5,7,11,13,17,19,23} see A147581

%H Amiram Eldar, <a href="/A147579/b147579.txt">Table of n, a(n) for n = 1..10000</a>

%F Sum_{n>=1} 1/a(n) = 1/92160. - _Amiram Eldar_, Dec 22 2020

%t a = {}; Do[If[EulerPhi[255255 x] == 92160 x, AppendTo[a, 255255 x]], {x, 1, 100}]; a

%Y Cf. A060735, A143207, A147571-A147575, A147576-A147580.

%K nonn

%O 1,1

%A _Artur Jasinski_, Nov 07 2008

%E More terms from _Amiram Eldar_, Mar 11 2020