A214700 Numbers n such that 9^n + 3^(n+1) - 1 is prime.

1, 2, 3, 4, 8, 21, 22, 31, 45, 86, 99, 127, 239, 264, 332, 338, 752, 793, 2310, 4364, 7454, 14788, 20031

Offset

1,2

Comments

no more n<30000

A214700(n) = i when A214730(i)=3

Links

Table of n, a(n) for n=1..23.

Prog

PFGW and SCRIPTIFY
SCRIPT
DIM nn, 0
DIMS tt
OPENFILEOUT myfile, a(n)
LABEL loopn
SET nn, nn+1
IF nn>30000 THEN END
SETS tt, %d\ ; nn
PRP (3^nn+3)*3^nn-1, tt
IF ISPRP THEN GOTO a
IF ISPRIME THEN GOTO a
GOTO loopn
LABEL a
WRITE myfile, tt
GOTO loopn
(PARI) is(n)=ispseudoprime(9^n+3^(n+1)-1) \\ Charles R Greathouse IV, Jun 06 2017

Crossrefs

Cf. A214730.

Sequence in context: A105055 A108506 A129284 * A100997 A368989 A128657

Adjacent sequences: A214697 A214698 A214699 * A214701 A214702 A214703

Keyword

nonn

Author

Pierre CAMI, Jul 26 2012

Status

approved