The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A147574

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A147574

Numbers with exactly 7 distinct prime divisors {2,3,5,7,11,13,17}.
(history; published version)

#18 by Michel Marcus at Thu Nov 12 10:34:56 EST 2020

STATUS

reviewed

approved

#17 by Joerg Arndt at Thu Nov 12 10:10:19 EST 2020

STATUS

proposed

reviewed

#16 by Michel Marcus at Thu Nov 12 03:47:12 EST 2020

STATUS

editing

proposed

#15 by Michel Marcus at Thu Nov 12 03:47:09 EST 2020

COMMENTS

Successive numbers k such that EulerPhi[(x])/x = m:

STATUS

proposed

editing

#14 by Amiram Eldar at Thu Nov 12 03:37:44 EST 2020

STATUS

editing

proposed

#13 by Amiram Eldar at Thu Nov 12 03:33:35 EST 2020

FORMULA

Sum_{n>=1} 1/a(n) = 1/92160. - Amiram Eldar, Nov 12 2020

STATUS

approved

editing

#12 by OEIS Server at Tue Mar 10 10:24:56 EDT 2020

LINKS

Amiram Eldar, <a href="/A147574/b147574_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)

#11 by Susanna Cuyler at Tue Mar 10 10:24:56 EDT 2020

STATUS

proposed

approved

Discussion

Tue Mar 10

10:24

OEIS Server: Installed new b-file as b147574.txt.  Old b-file is now b147574_1.txt.

#10 by Amiram Eldar at Tue Mar 10 10:23:51 EDT 2020

STATUS

editing

proposed

#9 by Amiram Eldar at Tue Mar 10 10:21:11 EDT 2020

FORMULA

a(n) = 510510 * A080681(n). - Amiram Eldar, Mar 10 2020

MATHEMATICA

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

CROSSREFS

Cf. A060735, A080681, A143207, A147571-A147575, A147576-A147580.