The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A203967

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A203967

The number of positive integers <= n that have a prime number of divisors.
(history; published version)

#16 by Charles R Greathouse IV at Sun Aug 03 14:01:37 EDT 2014

MATHEMATICA

tot = 0; Table[If[PrimeQ[DivisorSigma[0, n]], tot++]; tot, {n, 100}] (* _T. D. Noe, _, Jan 10 2012 *)

Discussion

Sun Aug 03

14:01

OEIS Server: https://oeis.org/edit/global/2267

#15 by OEIS Server at Thu Jun 06 13:20:57 EDT 2013

LINKS

Reinhard Zumkeller, <a href="/A203967/b203967_1.txt">Table of n, a(n) for n = 1..10000</a>

#14 by T. D. Noe at Thu Jun 06 13:20:57 EDT 2013

STATUS

editing

approved

Discussion

Thu Jun 06

13:20

OEIS Server: Installed new b-file as b203967.txt.  Old b-file is now b203967_1.txt.

#13 by Reinhard Zumkeller at Thu Jun 06 12:54:58 EDT 2013

FORMULA

a(n) = a(n-1) + A010055(n) * A010051(A100995(n)), a(+1) = 0. - Reinhard Zumkeller, Jun 05 06 2013

PROG

a203967 n = length $ takeWhile (<= n) a050376_a009087_list

-- Reinhard Zumkeller, Jun 05 06 2013

CROSSREFS

Cf. A050376.

Discussion

Thu Jun 06

13:03

Reinhard Zumkeller: My changes #8 and #9 from yesterday were wrong. Thanks to Tony Noe who notified me. I apologize. I repaired my faulty contributions: %S, %H (b-file), %F and %o.  Further I deleted the inapplicable %E.

13:20

T. D. Noe: Thank you!

#12 by Reinhard Zumkeller at Thu Jun 06 12:50:13 EDT 2013

LINKS

Reinhard Zumkeller, <a href="/A203967/b203967_1.txt">Table of n, a(n) for n = 1..10000</a>

#11 by Reinhard Zumkeller at Thu Jun 06 12:48:37 EDT 2013

DATA

0, 1, 2, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 8, 9, 10, 10, 11, 11, 11, 11, 12, 12, 13, 13, 13, 13, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 25, 25, 25

LINKS

Reinhard Zumkeller, <a href="/A203967/b203967.txt">Table of n, a(n) for n = 1..10000</a>

EXTENSIONS

Data corrected for n > 63 by Reinhard Zumkeller, Jun 05 2013

STATUS

approved

editing

#10 by T. D. Noe at Thu Jun 06 02:23:10 EDT 2013

STATUS

editing

approved

#9 by Reinhard Zumkeller at Wed Jun 05 23:26:38 EDT 2013

FORMULA

a(n) = a(n-1) + A010051(A100995(n)), a(1) = 0. - Reinhard Zumkeller, Jun 05 2013

PROG

(Haskell)

a203967 n = length $ takeWhile (<= n) a050376_list

-- Reinhard Zumkeller, Jun 05 2013

CROSSREFS

Cf. A050376.

Discussion

Wed Jun 05

23:32

Reinhard Zumkeller: n=64=2^6 and 6 is not prime, therefore a(64)=a(63)+0=23<>24.

#8 by Reinhard Zumkeller at Wed Jun 05 23:25:32 EDT 2013

DATA

LINKS

Reinhard Zumkeller, <a href="/A203967/b203967.txt">Table of n, a(n) for n = 1..10000</a>

EXTENSIONS

Data corrected for n > 63 by Reinhard Zumkeller, Jun 05 2013

STATUS

approved

editing

#7 by Russ Cox at Fri Mar 30 17:23:11 EDT 2012

AUTHOR

_Geoffrey Critzer (critzer.geoffrey(AT)usd443.org), _, Jan 08 2012

Discussion

Fri Mar 30

17:23

OEIS Server: https://oeis.org/edit/global/123