OFFSET
1,2
COMMENTS
Let K be the number of entries in the sequence less than or equal to M. Then the ratio K/M is nearly monotone decreasing. I do not know if the sequence converges, but if it does, it will be to a number less than 0.30.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
35 is a term because 35^2 + 35 + 37 = 1297, which is prime.
MAPLE
filter:= select(n -> isprime(n^2+n+nextprime(n+1)), [$1..200]); # Robert Israel, Aug 10 2018
MATHEMATICA
Select[Range[200], PrimeQ[(NextPrime[# + 1] + #^2 + #)] &] (* Vincenzo Librandi, Aug 11 2018 *)
PROG
(PARI) isok(n) = isprime(n^2 + n + nextprime(n+2)); \\ Michel Marcus, Aug 11 2018
(Magma)[n: n in [1..200] | IsPrime(n^2 + n + NextPrime(n+1))]; // Vincenzo Librandi, Aug 11 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Michael V. Scovetta (mike(AT)scovetta.com), Apr 12 2002
EXTENSIONS
1 inserted, and definition corrected by Robert Israel, Aug 10 2018
STATUS
approved