Search: id:A129309
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%I A129309
%S A129309 1,1,3,3,2,3,4,4,5,5,6,6,6,7,8,7,8,7,7,10,9,9,9,9,10,10,10,10,12,12,12,
%T A129309 13,14,13,13,13,14,14,14,14,14,14,16,16,17,16,15,17,17,16,18,19,19,19,
%U A129309 19,18,20,21,20,20,21,21,21,21,21,22,22,22,22,22,22,23,23,23,23,25,24
%N A129309 a(n) = number of primes which are < c(n) and are coprime to c(n), where 
               c(n) is the n-th composite.
%H A129309 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%F A129309 a(n) = A048865(A002808(n)) = A000720(A002808(n)) - A001221(A002808(n)).
%p A129309 A002808 := proc(n) local resul,i ; i := 1 ; resul := 4 ; while i < n 
               do resul := resul+1 ; while isprime(resul) do resul := resul+1 ; 
               od ; i := i+1 ; od; RETURN(resul) ; end: A000720 := proc(n) numtheory[pi](n) 
               ; end: A001221 := proc(n) nops(numtheory[factorset](n)) ; end: A048865 
               := proc(n) A000720(n)-A001221(n) ; end: A129309 := proc(n) A048865(A002808(n)) 
               ; end: seq(A129309(n),n=1..80) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Jun 15 2007
%Y A129309 Cf. A048865.
%Y A129309 Sequence in context: A079063 A031352 A057853 this_sequence A003560 A123676 
               A122775
%Y A129309 Adjacent sequences: A129306 A129307 A129308 this_sequence A129310 A129311 
               A129312
%K A129309 nonn
%O A129309 1,3
%A A129309 Leroy Quet May 26 2007
%E A129309 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 15 2007

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