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Number of primes which are the difference between two triangular numbers, where the smaller is the n-th triangular number.

+0
3

1, 1, 2, 0, 2, 1, 1, 1, 1, 0, 2, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 2, 0, 0, 1, 0, 0, 2, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 2, 0, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 2, 1, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 2, 0, 0, 1, 0, 0, 2, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1 (list; graph; listen)

	OFFSET	`0,3`
	FORMULA	`a(n)=2 if both n+1 is prime and 2n+3 is prime, =1 if one of n+1 and 2n+3 is prime, =0 if neither are primes.`
	EXAMPLE	`a(4)=2 because 4th triangular number is 10 and both 15-10=5 and 21-10=11 are primes.`
	CROSSREFS	`Cf. A000217, A001227, A056563, A056564.` `Sequence in context: A112553 A026610 A094451 this_sequence A135220 A068320 A111330` `Adjacent sequences: A056559 A056560 A056561 this_sequence A056563 A056564 A056565`
	KEYWORD	`nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Jun 27 2000`

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Last modified November 29 12:46 EST 2009. Contains 167659 sequences.

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