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Characteristic function of Sophie Germain primes.

+0
14

0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 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, 1, 0, 0, 0, 0, 0, 0, 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, 1, 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 2*n+1 is prime then 1 else 0; a(A005384(n)) = 1; a(A138887(n)) = 0; a(A053176(n)) = 0.` `A156874(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, Sophie Germain prime`
	FORMULA	`a(n) = A010051(n)A010051(2n+1).`
	CROSSREFS	`A156659.` `Sequence in context: A091225 A132380 A021913 this_sequence A155899 A117814 A062301` `Adjacent sequences: A156657 A156658 A156659 this_sequence A156661 A156662 A156663`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 13 2009`
	EXTENSIONS	`Definition corrected by Daniel Forgues (squid(AT)zensearch.com), Aug 04 2009`

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.

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