A237527 - OEIS

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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.

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