id:A129309 - OEIS Search Results

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a(n) = number of primes which are < c(n) and are coprime to c(n), where c(n) is the n-th composite.

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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, 13, 14, 13, 13, 13, 14, 14, 14, 14, 14, 14, 16, 16, 17, 16, 15, 17, 17, 16, 18, 19, 19, 19, 19, 18, 20, 21, 20, 20, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 25, 24 (list; graph; listen)

	OFFSET	`1,3`
	LINKS	`Leroy Quet, Home Page (listed in lieu of email address)`
	FORMULA	`a(n) = A048865(A002808(n)) = A000720(A002808(n)) - A001221(A002808(n)).`
	MAPLE	`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`
	CROSSREFS	`Cf. A048865.` `Sequence in context: A079063 A031352 A057853 this_sequence A003560 A123676 A122775` `Adjacent sequences: A129306 A129307 A129308 this_sequence A129310 A129311 A129312`
	KEYWORD	`nonn`
	AUTHOR	`Leroy Quet May 26 2007`
	EXTENSIONS	`More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 15 2007`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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