A075899 Primes of the form 3^n + n^2.

13, 97, 59149, 31381060093, 12157665459056930401

Offset

1,1

Comments

The next term (a(6)) has 146 digits; a(7) has 755 digits. - Harvey P. Dale, May 21 2013

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..7

Mathematica

f[n_]:=3^n+n^2; lst={}; Do[If[PrimeQ[f[n]], AppendTo[lst, f[n]]], {n, 3*5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Jul 24 2009 *)
Select[Table[3^n+n^2, {n, 0, 2000}], PrimeQ] (* Harvey P. Dale, May 21 2013 *)

Prog

(PARI) list(lim)=my(v=List(), t); forstep(n=2, logint(lim\1, 3), 2, if(ispseudoprime(t=3^n+n^2) && t<=lim, listput(v, t))); Vec(v) \\ Charles R Greathouse IV, Sep 14 2015
(PARI) is(n)=my(e=logint(n, 3)); e%2==0 && n==3^e+e^2 && isprime(n) \\ Charles R Greathouse IV, Sep 14 2015

Crossrefs

Cf. A075898 (for the corresponding n).

Sequence in context: A126508 A228680 A158795 * A006976 A282992 A295271

Adjacent sequences: A075896 A075897 A075898 * A075900 A075901 A075902

Keyword

nonn

Author

Zak Seidov, Oct 17 2002

Extensions

a(6) (moved to b-file) from Vladimir Joseph Stephan Orlovsky, Jul 24 2009

Status

approved