id:A059396 - OEIS Search Results

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Number of primes less than square root of n-th prime; i.e. number of trial divisions by smaller primes to show that n-th prime is indeed prime.

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0, 0, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9 (list; graph; listen)

	OFFSET	`0,5`
	COMMENT	`Perhaps close to 2*(n/loge(n))^(1/2)`
	FORMULA	`a(n) = A000720(A000196(A000040(n)))`
	EXAMPLE	`a(32) = 5 since the 32nd prime is 131 which is not divisible by 2, 3, 5, 7 or 11 (and does not need to be tested against 13, 17, 19 etc. since 13^2 = 169>131).`
	CROSSREFS	`Sequence in context: A023968 A000196 A111850 this_sequence A108602 A085290 A108611` `Adjacent sequences: A059393 A059394 A059395 this_sequence A059397 A059398 A059399`
	KEYWORD	`nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Jan 29 2001`

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

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