id:A128815 - OEIS Search Results

Search: id:A128815

Displaying 1-1 of 1 results found.

page 1

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

+0
1

1, 2, 4, 5, 7, 11, 13, 14, 16, 19, 20, 23, 26, 32, 37, 40, 49, 53, 56, 58, 61, 65, 68, 70, 74, 76, 77, 79, 88, 89, 98, 100, 104, 109, 110, 116, 118, 130, 137, 140, 142, 146, 149, 152, 154, 160, 161, 163, 166, 167, 172, 175, 187, 188, 191, 193, 202, 205, 208, 214, 217 (list; graph; listen)

	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.` `Sequence in context: A082741 A099522 A108464 this_sequence A056527 A147991 A033160` `Adjacent sequences: A128812 A128813 A128814 this_sequence A128816 A128817 A128818`
	KEYWORD	`nonn`
	AUTHOR	`Zak Seidov (zakseidov(AT)gmail.com), Apr 10 2007`

page 1

Search completed in 0.002 seconds

Last modified December 6 22:55 EST 2009. Contains 170429 sequences.

AT&T Labs Research