A167595 The number of nonisolated primes between the n-th nonisolated nonprime and the n-th isolated nonprime.

1, 2, 1, 3, 5, 5, 7, 9, 9, 11, 13, 15, 17, 19, 21, 23, 23, 25, 27, 29, 31, 33, 35, 37, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 61, 63, 65, 67, 69, 71, 73, 75, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 119

Offset

1,2

Links

Table of n, a(n) for n=1..69.

Example

a(1)=1  (0 < 3 < 4);
a(2)=2  (1 < 3,5 < 6);
a(3)=1  (8 < 11 <12);
a(4)=3  (9 < 11,13,17 < 18);
a(5)=5 (10 < 11,13,17,19,29 < 30);
a(6)=5 (14 < 17,19,29,31,41 < 42);
a(7)=7 (15 < 17,19,29,31,41,43,59 < 60);
a(8)=9 (16 < 17,19,29,31,41,43,59,61,71 < 72).

Maple

A164276 := proc(n) option remember; if n = 1 then 0; else for a from procname(n-1)+1 do if isA164276(a) then return a; end if; end do; end if: 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:
A167595 := proc(n) a := 0 ; for k from A164276(n)+1 to A014574(n)-1 do if isA001097(k) then a := a+1 ; end if; end do: a ; end proc:
seq(A167595(n), n=1..120) ; # R. J. Mathar, May 30 2010

Crossrefs

Cf. A001097 (the nonisolated primes), A014574 (the isolated nonprimes), A164276 (the nonisolated nonprimes), A167511.

Sequence in context: A137655 A355621 A296064 * A328600 A179382 A161169

Adjacent sequences: A167592 A167593 A167594 * A167596 A167597 A167598

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Nov 06 2009

Extensions

More terms from R. J. Mathar, May 30 2010

Status

approved