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A237527 Numbers n of the form p^2-p-1 = A165900(p), for prime p, such that n^2-n-1 = A165900(n) is also prime. 3
5, 155, 505, 2755, 3421, 6805, 11341, 27721, 29755, 31861, 44309, 49505, 52211, 65791, 100171, 121451, 134321, 185329, 195805, 236681, 252505, 258571, 292139, 325469, 375155, 380071, 452255, 457651, 465805, 563249, 676505, 1041419, 1061929 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All numbers are congruent to 1 mod 10, 5 mod 10, or 9 mod 10.

A subsequence of A165900 and A028387. - M. F. Hasler, Mar 01 2014

LINKS

Table of n, a(n) for n=1..33.

FORMULA

a(n) = A165900(A230026(n)). - M. F. Hasler, Mar 01 2014

EXAMPLE

5 = 3^2-3-1 (3 is prime) and 5^2-5-1 = 19 is also prime. So, 5 is a member of this sequence.

PROG

(Python)

import sympy

from sympy import isprime

{print(n**2-n-1) for n in range(10**4) if isprime(n) and isprime((n**2-n-1)**2-(n**2-n-1)-1)}

(PARI) s=[]; forprime(p=2, 40000, n=p^2-p-1; if(isprime(n^2-n-1), s=concat(s, n))); s \\ Colin Barker, Feb 10 2014

CROSSREFS

Cf. A237360, A039914, A002327.

Sequence in context: A322634 A108535 A265123 * A015019 A225165 A151577

Adjacent sequences:  A237524 A237525 A237526 * A237528 A237529 A237530

KEYWORD

nonn

AUTHOR

Derek Orr, Feb 09 2014

STATUS

approved

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Last modified May 22 09:50 EDT 2022. Contains 353949 sequences. (Running on oeis4.)