OFFSET
1,1
COMMENTS
Conjecture: 2^a(n)-1 is not prime; in other words, these primes are included in A054723.
2*a(n) + 679 is a square. - Vincenzo Librandi, Apr 10 2015
Equivalently, primes of the form 36*n^2 + 36*n + 9. - Charles R Greathouse IV, Jul 24 2024
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..3000
FORMULA
a(n) >> n^2 log n. - Charles R Greathouse IV, Jul 24 2024
MATHEMATICA
Select[Table[2 n^2 + 54 n + 25, {n, 500}], PrimeQ]
PROG
(Magma) [a: n in [1..500] | IsPrime(a) where a is 2*n^2+54*n+25];
(PARI) list(lim)=my(v=List()); for(n=2, (sqrtint(lim\1*2+679)-27)\6, my(p=18*n^2 + 162*n + 25); if(isprime(p), listput(v, p))); Vec(v) \\ Charles R Greathouse IV, Jul 24 2024
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 09 2012
STATUS
approved