A161676 - OEIS

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A161676

Isolated primes p such that 2^p-1 is also a prime number.

2, 89, 127, 607, 2203, 2281, 3217, 4253, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	FORMULA	`A000043 INTERSECT A007510.`
	EXAMPLE	`For the isolated prime p=2= A007510(1), p^2-1=3 is prime, which adds p=2 to the sequence.`
	MAPLE	`MP := [2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917]:` n := 0: for j to 39 do if `and`(isprime(MP[j]-2) = false, isprime(MP[j]+2) = false) then n := n+1; a[n] := MP[j] else end if end do: `seq(a[n], n = 1 .. 25); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 20 2009]`
	CROSSREFS	`Cf. A000043, A007510.` `Sequence in context: A058459 A105268 A139881 * A023302 A041967 A024239` `Adjacent sequences: A161673 A161674 A161675 * A161677 A161678 A161679`
	KEYWORD	`nonn`
	AUTHOR	`Vladislav-Stepan Malakhovsky & Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jun 16 2009`
	EXTENSIONS	`More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 20 2009` `Definition rephrased by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 23 2009`

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Last modified February 15 18:22 EST 2012. Contains 205835 sequences.