%I A139636
%S A139636 3,5,6,7,8,11,9,10,12,13,14,17,15,16,18,19,20,23,21,22,24,29,25,26,27,
%T A139636 28,30,31,32,37,33,34,35,36,38,41,39,40,42,43,44,47,45,46,48,53,49,50,
%U A139636 51,52,54,59,55,56,57,58,60,61,62,67,63,64,65,66,68,71,69,70,72,73,74
%N A139636 If n = the kth prime, then a(n) = the (k+1)th prime. If n = the kth composite, 
               then a(n) = the (k+1)th composite.
%C A139636 This is a permutation of the positive integers sans 1,2,4.
%H A139636 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%p A139636 A000040 := proc(n) ithprime(n) ; end: A002808 := proc(n) local a; if 
               n = 1 then 4; else for a from A002808(n-1)+1 do if not isprime(a) 
               then RETURN(a) ; fi ; od: fi ; end: A066246 := proc(n) local k ; 
               if isprime(n) then 0 ; else for k from 1 do if A002808(k) = n then 
               RETURN(k) ; fi ; od: fi ; end: A049084 := proc(n) if not isprime(n) 
               then 0; else numtheory[pi](n) ; fi ; end: A139636 := proc(n) local 
               k; if isprime(n) then k := A049084(n) ; RETURN(A000040(k+1)) ; else 
               k := A066246(n) ; RETURN(A002808(k+1)) ; fi ; end: seq(A139636(n),
               n=2..160) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 12 
               2008
%Y A139636 Cf. A139637.
%Y A139636 Sequence in context: A039041 A079253 A076054 this_sequence A159559 A047583 
               A010906
%Y A139636 Adjacent sequences: A139633 A139634 A139635 this_sequence A139637 A139638 
               A139639
%K A139636 nonn
%O A139636 2,1
%A A139636 Leroy Quet Apr 28 2008
%E A139636 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 12 2008