id:A105173 - OEIS Search Results

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Numbers n such that either n*(n+1)/4 + 1 or n*(n+1)/4 - 1 or both are primes.

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3, 7, 8, 15, 16, 23, 24, 32, 39, 40, 47, 48, 55, 56, 63, 64, 71, 79, 80, 87, 95, 103, 104, 111, 112, 119, 120, 128, 135, 136, 143, 151, 152, 159, 167, 175, 176, 183, 199, 208, 216 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`The primes are = (sum of numbers from 1 to n)/2 + or - 1`
	EXAMPLE	`34/4=3 3-1=2 prime so a(1)=3` `78/4=14 14-1=13 prime so a(2)=7` `8*9/4=18 18-1=17 prime 18+1=19 prime so a(3)=8`
	CROSSREFS	`Sequence in context: A002381 A131559 A051211 this_sequence A076683 A045542 A031404` `Adjacent sequences: A105170 A105171 A105172 this_sequence A105174 A105175 A105176`
	KEYWORD	`nonn`
	AUTHOR	`Pierre CAMI (pierrecami(AT)tele2.fr), Apr 11 2005`

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Last modified July 24 12:00 EDT 2008. Contains 142294 sequences.

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