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A176811 Number of primes between 2*(lesser of n-th twin prime pair) and 2*(greater of n-th twin prime pair). 1
1, 2, 1, 1, 2, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 2, 2, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 2, 1, 0, 0, 1, 1, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 2, 1, 0, 2, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Number of primes between 2*A001359(n) and 2*A006512(n).

Number of primes between A108605(n) and A176810(n).

Number of primes between 2*A077800(2n-1) and 2*A077800(2n).

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

a(1)=1 because 2*3 < 7 (prime) < 2*5;

a(2)=2 because 2*5 < 11 (prime) < 13(prime) < 2*7;

a(3)=1 because 2*11 < 23 (prime) < 2*13.

MAPLE

A001359 := proc(n) option remember; if n = 1 then 3; else for a from procname(n-1)+2 by 2 do if isprime(a) and isprime(a+2) then return a; end if; end do: end if; end proc:

A006512 := proc(n) A001359(n)+2 ; end proc:

A176811 := proc(n) numtheory[pi](2*A006512(n)) - numtheory[pi](2*A001359(n)) ; end proc:

seq(A176811(n), n=1..120) ; # R. J. Mathar, Apr 27 2010

CROSSREFS

Cf. A001359, A006512, A077800, A108605, A176810.

Sequence in context: A117586 A307988 A268917 * A057594 A259029 A286128

Adjacent sequences:  A176808 A176809 A176810 * A176812 A176813 A176814

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Apr 26 2010

EXTENSIONS

Terms corrected starting at a(34) by R. J. Mathar, Apr 27 2010

STATUS

approved

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Last modified January 18 19:50 EST 2020. Contains 331030 sequences. (Running on oeis4.)