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A220789
Numbers n such that 2*prime(n)^2 - 1 is not prime.
1
3, 8, 9, 10, 11, 12, 15, 16, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 32, 34, 35, 36, 38, 39, 40, 43, 44, 48, 49, 50, 51, 52, 53, 55, 57, 58, 60, 61, 63, 65, 66, 67, 68, 69, 70, 72, 74, 76, 77, 78, 79, 82, 83, 85, 86, 87, 88, 89, 90, 91, 92, 94, 95, 96, 97, 98, 99, 100
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[200], !PrimeQ[2Prime[#]^2 - 1]&]
PROG
(Magma) [n: n in [1..220]| not IsPrime(2*NthPrime(n)^2-1)];
CROSSREFS
Sequence in context: A154927 A348297 A363955 * A276006 A091767 A024549
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Jan 18 2013
STATUS
approved