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A100712
Numbers n such that n*(n-1)-1 and n*(n+1)+1 are both primes.
1
3, 5, 6, 12, 14, 17, 20, 21, 27, 54, 57, 66, 69, 71, 77, 90, 101, 131, 141, 150, 155, 161, 164, 189, 192, 194, 231, 245, 266, 332, 336, 344, 351, 381, 392, 402, 434, 456, 476, 495, 500, 512, 531, 551, 572, 579, 582, 605, 626, 671, 677, 696, 747, 755, 762, 782, 839
OFFSET
1,1
LINKS
MAPLE
select(n -> isprime(n*(n-1)-1) and isprime(n*(n+1)+1), [$1..1000]); # Robert Israel, Jan 04 2018
MATHEMATICA
Select[Range[6! ], PrimeQ[ #^2-(#+1)]&&PrimeQ[ #^2+(#+1)]&] (* Vladimir Joseph Stephan Orlovsky, Dec 19 2009 *)
CROSSREFS
Sequence in context: A280590 A356709 A185912 * A086187 A088082 A238961
KEYWORD
easy,nonn
AUTHOR
Pierre CAMI, Dec 10 2004
EXTENSIONS
a(54)=755 inserted by Robert Israel, Jan 04 2018
STATUS
approved