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A147574 Numbers with exactly 7 distinct prime divisors {2,3,5,7,11,13,17} 5
510510, 1021020, 1531530, 2042040, 2552550, 3063060, 3573570, 4084080, 4594590, 5105100, 5615610, 6126120, 6636630, 7147140, 7657650, 8168160, 8678670, 9189180, 10210200, 10720710, 11231220, 12252240, 12762750, 13273260, 13783770 (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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MATHEMATICA

a = {}; Do[If[EulerPhi[x 510510] == 92160 x, AppendTo[a, 510510 x]], {x, 1, 100}]; a (*Artur Jasinski*)

sdpdQ[n_]:=Module[{f=FactorInteger[n][[All, 1]]}, Length[f]==7&&Max[f]==17]; Select[Range[510510, 138*10^5, 510510], sdpdQ] (* Harvey P. Dale, Aug 03 2019 *)

CROSSREFS

A060735, A143207, A147571-A147575, A147576-A147580

Sequence in context: A176655 A123321 A258362 * A046325 A136352 A138207

Adjacent sequences:  A147571 A147572 A147573 * A147575 A147576 A147577

KEYWORD

nonn

AUTHOR

Artur Jasinski, Nov 07 2008

STATUS

approved

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Last modified September 19 15:24 EDT 2019. Contains 327198 sequences. (Running on oeis4.)