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A237642 Primes of the form n^2-n-1 (for some n) such that p^2-p-1 is also prime. 4
5, 11, 29, 71, 131, 181, 379, 419, 599, 1979, 2069, 3191, 4159, 13339, 14519, 17291, 19739, 20879, 21169, 26731, 30449, 31151, 39799, 48619, 69959, 70489, 112559, 122849, 132859, 139501, 149381, 183611, 186191, 198469, 212981, 222311, 236681 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Except a(1), all numbers are congruent to 1 mod 10 or 9 mod 10.

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

11 is prime and equals 4^2-4-1, and 11^2-11-1 = 109 is prime. So, 11 is a member of this sequence.

PROG

(Python)

import sympy

from sympy import isprime

{print(n**2-n-1) for n in range(10**3) if isprime(n**2-n-1) and isprime((n**2-n-1)**2-(n**2-n-1)-1)}

(PARI)

s=[]; for(n=1, 1000, p=n^2-n-1; if(isprime(p) && isprime(p^2-p-1), s=concat(s, p))); s \\ Colin Barker, Feb 11 2014

CROSSREFS

Cf. A002327, A091568.

Sequence in context: A129780 A154504 A106060 * A059508 A084817 A183382

Adjacent sequences:  A237639 A237640 A237641 * A237643 A237644 A237645

KEYWORD

nonn

AUTHOR

Derek Orr, Feb 10 2014

STATUS

approved

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Last modified May 16 22:37 EDT 2022. Contains 353724 sequences. (Running on oeis4.)