OFFSET
1,1
COMMENTS
Excluding a(1), these are also the bases in which 321 represents a prime number.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[500], PrimeQ[1+2#+3#^2]&] (* Harvey P. Dale, Jun 23 2012 *)
PROG
(PARI) is(n)=isprime(1+2*n+3*n^2) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Aug 28 2003
STATUS
approved