login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A161961 Denominator of ratio in lowest terms of pi(n^2)/(n*pi(n)), where pi(x) = A000720(x). 2
1, 3, 4, 5, 18, 28, 16, 18, 8, 11, 30, 2, 21, 15, 16, 119, 21, 19, 80, 168, 44, 23, 72, 75, 117, 81, 252, 145, 150, 341, 88, 363, 374, 77, 66, 148, 2, 39, 480, 533, 273, 602, 616, 35, 644, 15, 40, 35, 750, 85, 260, 848, 864, 440, 896, 912, 464, 1003, 1020, 366, 279, 126, 96, 585 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

Conjecture: S(n) = pi(n^2)/(n*pi(n)) ~ 1/2.

LINKS

Table of n, a(n) for n=2..65.

EXAMPLE

The first few fractions S(n) are 1, 2/3, 3/4, 3/5, 11/18, 15/28, 9/16, 11/18, 5/8, ...

MAPLE

A000720 := proc(n) numtheory[pi](n) ; end:

A161961 := proc(n) A000720(n^2)/n/A000720(n) ; denom(%) ; end: seq(A161961(n), n=2..120) ; # R. J. Mathar, Oct 05 2009

MATHEMATICA

Table[PrimePi[n^2]/(n*PrimePi[n]), {n, 1, 100}]

CROSSREFS

Cf. A161960, A000720.

Sequence in context: A263810 A249541 A059184 * A161474 A247573 A084930

Adjacent sequences:  A161958 A161959 A161960 * A161962 A161963 A161964

KEYWORD

nonn,frac,less

AUTHOR

Daniel Tisdale, Jun 22 2009

EXTENSIONS

Keyword:frac added by R. J. Mathar, Jun 30 2009

Definition corrected and sequence extended by R. J. Mathar, Oct 05 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 22 20:51 EDT 2019. Contains 325226 sequences. (Running on oeis4.)