%I A162308
%S A162308 0,7,9,11,11,13,15,15,15,15,19,19,19,23,23,23,23,29,29,31,33,33,33,35,
%T A162308 37,37,39,39,39,41,41,41,41,41,41,41,41,41,41,45,45,45,45,47,47,47,47,
%U A162308 47,47,47,49,49,49,49,51,51,51,53,53,55,57,57,59,59,59,59,59,59,59
%N A162308 Number of twin primes A001097 smaller than the non-twin prime A007510(n).
%e A162308 a(2)=7 counts the numbers 3, 5, 7, 11, 13, 17, 19 below 23=A007510(2).
%p A162308 isA007510 := proc(n) RETURN(isprime(n) and not isprime(n-2) and not isprime(n+2)) 
               ; end:
%p A162308 isA001097 := proc(n) RETURN(isprime(n) and (isprime(n-2) or isprime(n+2)) 
               ) ; end:
%p A162308 A007510 := proc(n) local a; if n = 1 then 2; else for a from procname(n-1)+1 
               do if isA007510(a) then RETURN(a) ; fi; od: fi; end:
%p A162308 A162308 := proc(n) local a,k; a := 0 ; for k from 3 to A007510(n)-1 do 
               if isA001097(k) then a := a+1; fi; od; a; end:
%p A162308 seq(A162308(n),n=1..120) ; # R. J. Mathar, Jul 02 2009
%Y A162308 Cf. A000040, A073425.
%Y A162308 Sequence in context: A117933 A112162 A058483 this_sequence A108815 A161992 
               A167377
%Y A162308 Adjacent sequences: A162305 A162306 A162307 this_sequence A162309 A162310 
               A162311
%K A162308 nonn
%O A162308 1,2
%A A162308 Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jul 01 2009
%E A162308 Edited by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 02 2009