id:A128815 - OEIS Search Results

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Numbers n such that n-th and (n+2)th triangular numbers sum up to a prime.

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	OFFSET	`1,2`
	COMMENT	`Or, numbers n such that 3+3n+n^2 is prime.`
	FORMULA	`Tr(n)+Tr(n+2) is prime; A000217(n)+A000217(n+2) is prime.`
	EXAMPLE	`7 is a term because 78/2+910/2=73 is prime;` `11 is a term because 1112/2+1314/2=157 is prime.`
	MATHEMATICA	`Select[Range[300], PrimeQ[3+3#+#^2]&]`
	CROSSREFS	`Cf. A000217.` `Adjacent sequences: A128812 A128813 A128814 this_sequence A128816 A128817 A128818` `Sequence in context: A082741 A099522 A108464 this_sequence A056527 A033160 A110924`
	KEYWORD	`nonn`
	AUTHOR	`Zak Seidov (zakseidov(AT)gmail.com), Apr 10 2007`

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Last modified October 6 12:54 EDT 2008. Contains 144667 sequences.

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