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A167529 a(n) is the number of nonisolated nonprimes k such that (n-th nonisolated prime) < k < (n-th isolated prime). 1
0, 9, 19, 22, 27, 34, 42, 37, 42, 41, 50, 50, 53, 64, 69, 49, 54, 79, 90, 72, 86, 82, 87, 74, 86, 90, 96, 106, 111, 98, 103, 102, 107, 88, 91, 88, 95, 73, 80, 73, 76, 22, 29, 26, 37, 21, 24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..81.

EXAMPLE

a(1)=0 (3 > [none] > 2);

a(2)=9 (5 < 8,9,10,14,15,16,20,21,22 < 23);

a(3)=19 (7 < 8,9,10,14,15,16,20,21,22,24,25,26,27,28,32,33,34,35,36 < 37).

MAPLE

isA001097 := proc(n) isprime(n) and ( isprime(n+2) or isprime(n-2) ); end proc:

A001097 := proc(n) option remember; if n =1 then 3; else for a from procname(n-1)+2 by 2 do if isA001097(a) then return a; end if; end do: end if; end proc:

A007510 := proc(n) option remember; if n <= 2 then op(n, [2, 23]) ; else for a from procname(n-1)+2 by 2 do if isprime(a) and not isprime(a+2) and not isprime(a-2) then return a; end if; end do: end if; end proc:

A167529 := proc(n) a := 0 ; for k from A001097(n)+1 to A007510(n)-1 do if isA164276(k) then a := a+1 ; end if; end do: a ; end proc:

seq(A167529(n), n=1..120) ; # R. J. Mathar, May 30 2010

CROSSREFS

Cf. A001097 (the nonisolated primes), A007510 (the isolated primes), A164276 (the nonisolated nonprimes), A167511.

Sequence in context: A242332 A075981 A079368 * A228610 A106677 A091592

Adjacent sequences:  A167526 A167527 A167528 * A167530 A167531 A167532

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Nov 06 2009

EXTENSIONS

Corrected (23 replaced with 22, 28 with 27) and extended by R. J. Mathar, May 30 2010

STATUS

approved

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Last modified July 13 17:54 EDT 2020. Contains 335689 sequences. (Running on oeis4.)