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

+0
3

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

	OFFSET	`0,4`
	FORMULA	`a(n)=2 if both n is prime and 2n-1 is prime, =1 if one of n and 2n-1 is prime, =0 if neither are primes.`
	EXAMPLE	`a(7)=2 because 7th triangular number is 28 and both 28-21=7 and 28-15=13 are primes.`
	CROSSREFS	`Cf. A000217, A001227, A056562, A056564.` `Sequence in context: A016541 A098876 A143277 this_sequence A088231 A143262 A035180` `Adjacent sequences: A056560 A056561 A056562 this_sequence A056564 A056565 A056566`
	KEYWORD	`nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Jun 27 2000`

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Last modified December 10 00:48 EST 2009. Contains 170565 sequences.

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