

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
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS



LINKS



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+n1)&&isprime(n^2+n+1), print1(n, ", "))) \\ Derek Orr, Dec 24 2015
(Magma) [n: n in [1..2*10^3] IsPrime(n^2+n1) and IsPrime(n^2+n+1)]; // Vincenzo Librandi, Dec 26 2015


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



EXTENSIONS

Corrected description from T. D. Noe, Jun 22 2004


STATUS

approved



