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 A147572 Numbers with exactly 5 distinct prime divisors {2,3,5,7,11}. 5
 2310, 4620, 6930, 9240, 11550, 13860, 16170, 18480, 20790, 23100, 25410, 27720, 32340, 34650, 36960, 41580, 46200, 48510, 50820, 55440, 57750, 62370, 64680, 69300, 73920, 76230, 80850, 83160, 92400, 97020, 101640, 103950, 110880, 113190, 115500, 124740, 127050 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Successive numbers k such that EulerPhi(x)/x = m: ( Family of sequences for successive n primes ) m=1/2 numbers with exactly 1 distinct prime divisor {2} see A000079 m=1/3 numbers with exactly 2 distinct prime divisors {2,3} see A033845 m=4/15 numbers with exactly 3 distinct prime divisors {2,3,5} see A143207 m=8/35 numbers with exactly 4 distinct prime divisors {2,3,5,7} see A147571 m=16/77 numbers with exactly 5 distinct prime divisors {2,3,5,7,11} see A147572 m=192/1001 numbers with exactly 6 distinct prime divisors {2,3,5,7,11,13} see A147573 m=3072/17017 numbers with exactly 7 distinct prime divisors {2,3,5,7,11,13,17} see A147574 m=55296/323323 numbers with exactly 8 distinct prime divisors {2,3,5,7,11,13,17,19} see A147575 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 FORMULA a(n) = 2310 * A051038(n). - Amiram Eldar, Mar 10 2020 Sum_{n>=1} 1/a(n) = 1/480. - Amiram Eldar, Nov 12 2020 MATHEMATICA a = {}; Do[If[EulerPhi[x]/x == 16/77, AppendTo[a, x]], {x, 1, 100000}]; a Select[Range, FactorInteger[#][[All, 1]]=={2, 3, 5, 7, 11}&] (* Harvey P. Dale, Oct 04 2020 *) CROSSREFS Cf. A051038, A060735, A143207, A147571-A147575, A147576-A147580. Sequence in context: A258360 A076252 A264718 * A046303 A046403 A288072 Adjacent sequences:  A147569 A147570 A147571 * A147573 A147574 A147575 KEYWORD nonn AUTHOR Artur Jasinski, Nov 07 2008 EXTENSIONS More terms from Amiram Eldar, Mar 10 2020 STATUS approved

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Last modified August 1 14:44 EDT 2021. Contains 346393 sequences. (Running on oeis4.)