The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A074398 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A074398

Number of primes between n and phi(n), with neither n nor phi(n) included in the count in case they are primes.
(history; published version)

#14 by N. J. A. Sloane at Sat Dec 16 22:41:43 EST 2017

STATUS

proposed

approved

#13 by Michael De Vlieger at Sat Dec 16 21:26:10 EST 2017

STATUS

editing

proposed

#12 by Michael De Vlieger at Sat Dec 16 21:25:46 EST 2017

MATHEMATICA

(* Second program: *)

Array[PrimePi@ # - PrimePi@ EulerPhi@ # - Boole@ PrimeQ@ # &, 96] (* or *) Array[Count[Range[EulerPhi@ # + 1, # - 1], _?PrimeQ] &, 96] (* Michael De Vlieger, Dec 16 2017 *)

STATUS

proposed

editing

#11 by Antti Karttunen at Sat Dec 16 15:48:05 EST 2017

STATUS

editing

proposed

#10 by Antti Karttunen at Sat Dec 16 15:44:42 EST 2017

NAME

Number of primes between n and phi(n), with neither n or nor phi(n) included in the count in case they are primes.

Discussion

Sat Dec 16

15:48

Antti Karttunen: Better now?

#9 by Antti Karttunen at Sat Dec 16 15:44:20 EST 2017

NAME

Number of primes between n and phi(n), with neither n or phi(n) included in the count in case they are primes.

COMMENTS

Number of primes in range (phi(n), n). - Antti Karttunen, Dec 16 2017.

EXTENSIONS

Name clarified by Antti Karttunen, Dec 16 2017

STATUS

proposed

editing

#8 by Antti Karttunen at Sat Dec 16 14:13:02 EST 2017

STATUS

editing

proposed

Discussion

Sat Dec 16

14:34

Michel Marcus: Maybe rather edit the name using your comment than add a comment?

#7 by Antti Karttunen at Sat Dec 16 14:12:37 EST 2017

KEYWORD

nonn,look,changed

#6 by Antti Karttunen at Sat Dec 16 14:11:55 EST 2017

COMMENTS

Number of primes in range (phi(n), n) . - Antti Karttunen, Dec 16 2017.

#5 by Antti Karttunen at Sat Dec 16 14:11:02 EST 2017

LINKS

Antti Karttunen, <a href="/A074398/b074398.txt">Table of n, a(n) for n = 1..16384</a>

FORMULA

a(n) = A085342(n) - A010051(n) = A000720(n) - A000720(A000010(n)) - A010051(n). - Antti Karttunen, Dec 16 2017