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A088485
Numbers n such that n^2 + n - 1 and n^2 + n + 1 are twin primes.
19
2, 3, 5, 6, 8, 15, 20, 21, 24, 38, 41, 50, 54, 59, 66, 89, 101, 131, 138, 141, 153, 155, 164, 176, 188, 203, 206, 209, 215, 218, 231, 236, 246, 288, 290, 309, 314, 351, 378, 395, 405, 453, 455, 456, 495, 500, 518, 530, 551, 560, 624, 644, 668, 686, 720, 728, 743, 761, 798, 825, 890, 915, 950, 974, 981
OFFSET
1,1
COMMENTS
A265006 gives these primes. - Derek Orr, Dec 24 2015
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..10000 (first 1000 terms from T. D. Noe)
EXAMPLE
20*20 + 20 - 1 = 419, 419 and 421 twin primes, 20 is the 7th of the sequence
MATHEMATICA
Select[Range[500], PrimeQ[ #^2+#-1] && PrimeQ[ #^2+#+1] &] (* T. D. Noe, Jun 22 2004 *)
Select[Range[1000], AllTrue[#^2+#+{1, -1}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jun 12 2017 *)
PROG
(PARI) for(n=1, 10^3, if(isprime(n^2+n-1)&&isprime(n^2+n+1), print1(n, ", "))) \\ Derek Orr, Dec 24 2015
(Magma) [n: n in [1..2*10^3] |IsPrime(n^2+n-1) and IsPrime(n^2+n+1)]; // Vincenzo Librandi, Dec 26 2015
CROSSREFS
Sequence in context: A239263 A216293 A088497 * A194626 A275323 A128994
KEYWORD
nonn,easy
AUTHOR
Pierre CAMI, Nov 09 2003
EXTENSIONS
Corrected description from T. D. Noe, Jun 22 2004
STATUS
approved