OFFSET
1,2
COMMENTS
There are 414 such primes for 1 <= x <= 1000, and 3280 for 1 <= x <= 10000.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
V. Granville, Quadratic progressions with very high prime density, MathOverflow.
FORMULA
a(n) = sqrt(A338476(n) + 1)/398.
EXAMPLE
a(3)=4 is in the sequence because 398*4^2 - 1 = 6367 is prime.
MAPLE
select(t -> isprime(398*t^2-1), [$1..1000]);
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Oct 29 2020
STATUS
approved