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A236056 Numbers n such that n^2 +/- n +/- 1 is prime for all four possibilities. 1
3, 6, 21, 456, 1365, 2205, 2451, 2730, 8541, 18486, 32199, 32319, 32781, 45864, 61215, 72555, 72561, 82146, 83259, 86604, 91371, 95199, 125334, 149331, 176889, 182910, 185535, 210846, 225666, 226254, 288420, 343161 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The only prime in this sequence is a(1) = 3.

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

1365^2+1365+1 (1864591), 1365^2-1365+1 (1861861), 1365^2+1365-1 (1864589), and 1365^2-1365-1 (1861859) are all prime. So 1365 is a member of this sequence.

PROG

(Python)

import sympy

from sympy import isprime

{print(p) for p in range(10**6) if isprime(p**2+p+1) and isprime(p**2-p+1) and isprime(p**2+p-1) and isprime(p**2-p-1)}

CROSSREFS

Numbers in the intersection of A002384, A045546, A055494, and A002328

Sequence in context: A019054 A066986 A096662 * A280116 A054297 A079514

Adjacent sequences:  A236053 A236054 A236055 * A236057 A236058 A236059

KEYWORD

nonn

AUTHOR

Derek Orr, Jan 18 2014

STATUS

approved

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Last modified June 24 11:11 EDT 2017. Contains 288697 sequences.