login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A159803 Number of primes p with (2m+1)^2 - 2m <= p < (2m+1)^2. 1
1, 1, 2, 2, 1, 3, 2, 3, 4, 4, 3, 5, 3, 5, 4, 4, 5, 2, 6, 4, 4, 7, 3, 8, 5, 7, 6, 5, 7, 8, 10, 5, 8, 7, 10, 8, 7, 10, 9, 7, 10, 9, 13, 10, 11, 11, 11, 11, 11, 12, 9, 9, 11, 14, 12, 11, 12, 12, 11, 15, 12, 11, 14, 12, 12, 14, 15, 12, 15, 14, 17, 18, 20, 18, 17, 14, 18, 12, 15, 15, 15, 14, 21 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

1) Immediate connection to unsolved problem, is there always a prime between n^2 and (n+1)^2 ("full" interval of two consecutive squares).

2) See sequence A145354 and A157884 for more details to this new improved conjecture.

3) Second ("right") half interval: number of primes p with (2m+1)^2-2m <= p < (2m+1)^2.

4) It is conjectured that a(m) >= 1.

5) No a(m) with m>5 is known, where a(m)=1.

This is a bisection of A094189 and hence related to a conjecture of Oppermann. - T. D. Noe, Apr 22 2009

REFERENCES

L. E. Dickson, History of the Theory of Numbers, Vol, I: Divisibility and Primality, AMS Chelsea Publ., 1999

R. K. Guy, Unsolved Problems in Number Theory (2nd ed.) New York: Springer-Verlag, 1994

P. Ribenboim, The New Book of Prime Number Records. Springer. 1996

LINKS

Table of n, a(n) for n=1..83.

EXAMPLE

1) m=1: 7 <= p < 9 => prime 7: a(1)=1.

2) m=2: 21 <= p < 25 => prime 23: a(2)=1.

3) m=3: 43 <= p < 49 => primes 43, 47: a(3)=2.

4) m=30: 3661 <= p < 3721 => primes 3671,3673,3677,3691,3697,3701,3709,3719: a(30)=8.

MAPLE

A159803 := proc(n) local a, p; a := 0 ; for p from 4*n^2+2*n+1 to 4*n^2+4*n do if isprime(p) then a := a+1 ; fi; od: a ; end: seq(A159803(n), n=1..120) ; # R. J. Mathar, Apr 22 2009

CROSSREFS

Cf. A145354, A157884, A014085.

Sequence in context: A071285 A289438 A008678 * A308934 A058741 A339491

Adjacent sequences:  A159800 A159801 A159802 * A159804 A159805 A159806

KEYWORD

nonn

AUTHOR

Ulrich Krug (leuchtfeuer37(AT)gmx.de), Apr 22 2009

EXTENSIONS

More terms from R. J. Mathar, Apr 22 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 June 24 05:09 EDT 2021. Contains 345416 sequences. (Running on oeis4.)