OFFSET
1,1
COMMENTS
Includes all primes == 2 (mod 5) or == 3 or 7 (mod 11) except 2 and 3.
If p is in this sequence, p^2 + p is not in A241884 although p^2 + p - 1 is composite.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
select(t -> isprime(t) and not isprime(t^2+t-1), [seq(i, i=1..1000, 2)]);
MATHEMATICA
Select[Prime[Range[100]], CompositeQ[#^2+#-1]&] (* Jean-François Alcover, Jul 18 2017 *)
PROG
(PARI) lista(nn) = forprime(p=2, nn, if (!isprime(p^2+p-1), print1(p, ", "))); \\ Michel Marcus, Jul 05 2017
(Magma) [p: p in PrimesUpTo(600) | not IsPrime(p^2+p-1)]; // Vincenzo Librandi, Jul 05 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Jul 04 2017
STATUS
approved