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Characteristic function of safe primes.

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13

0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; listen)

	OFFSET	`0,1`
	COMMENT	`a(n) = if n and also (n-1)/2 is prime then 1 else 0;` `a(A005385(n)) = 1; a(A156657(n)) = 0; a(A059456(n)) = 0.` `A156875(n) = SUM(a(k): 1<=k<=n). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 18 2009]`
	LINKS	`R. Zumkeller, Table of n, a(n) for n = 1..10000` `Index entries for characteristic functions` `Wikipedia, Safe prime`
	FORMULA	`a(n) = A010051(n)*A010051((n-1)/2).`
	CROSSREFS	`A156660.` `Sequence in context: A011672 A144194 A144196 this_sequence A011671 A086483 A011667` `Adjacent sequences: A156656 A156657 A156658 this_sequence A156660 A156661 A156662`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 13 2009`

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Last modified November 22 20:51 EST 2009. Contains 167312 sequences.

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