id:A156875 - OEIS Search Results

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Number of safe primes <= n.

+0
6

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

	OFFSET	`1,7`
	COMMENT	`a(n) = SUM(A156659(k): 1<=k<=n);` `a(n) = A156874(floor((n-1)\2)).`
	LINKS	`R. Zumkeller, Table of n, a(n) for n = 1..10000` `Wikipedia, Safe prime`
	EXAMPLE	`a(120) = #{5, 7, 11, 23, 47, 59, 83, 107} = 8.`
	CROSSREFS	`A005385, A156874, A156876, A156877, A156878, A000720.` `Sequence in context: A092139 A084558 A163291 this_sequence A066339 A052375 A074279` `Adjacent sequences: A156872 A156873 A156874 this_sequence A156876 A156877 A156878`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 18 2009`

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Last modified November 23 17:09 EST 2009. Contains 167438 sequences.

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