OFFSET
1,1
COMMENTS
Terms a(9) through a(12) have, respectively, 93, 94, 149, and 156 digits. - Harvey P. Dale, May 11 2013
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..15
MATHEMATICA
Select[Table[3^n+3n+1, {n, 0, 100}], PrimeQ] (* Harvey P. Dale, May 11 2013 *)
PROG
(PARI) for(i=0, 200, x=3^i+3*i+1; if(isprime(x), print1(x", ")))
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Graziano Aglietti (mg5055(AT)mclink.it), Aug 23 2010
EXTENSIONS
a(8) from Harvey P. Dale, May 11 2013
STATUS
approved