%I #6 Feb 21 2019 23:10:58
%S 2,89,127,607,2203,2281,3217,4253,9689,9941,11213,19937,21701,23209,
%T 44497,86243,216091,756839,859433,1257787,1398269,2976221,3021377,
%U 6972593,13466917
%N Isolated primes p such that 2^p-1 is also a prime number.
%F A000043 INTERSECT A007510.
%e For the isolated prime p=2= A007510(1), p^2-1=3 is prime, which adds p=2 to the sequence.
%p 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]:
%p 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:
%p seq(a[n], n = 1 .. 25); # _Emeric Deutsch_, Jun 20 2009
%Y Cf. A000043, A007510.
%K nonn
%O 1,1
%A Vladislav-Stepan Malakhovsky & _Juri-Stepan Gerasimov_, Jun 16 2009
%E More terms from _Emeric Deutsch_, Jun 20 2009
%E Definition rephrased by _R. J. Mathar_, Sep 23 2009
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