login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A058958 Numbers n such that 3^n + 4 is prime. 27
0, 1, 2, 3, 6, 9, 10, 22, 30, 42, 57, 87, 174, 195, 198, 562, 994, 2421, 2487, 4629, 5838, 13698, 14730, 16966, 25851, 98634, 117222, 192819, 226038, 296115 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Next term > 15000. The primes corresponding to 4629, ..., 14730 pass PARI's ispseudoprime() and the Rabin-Miller test for the first 100 prime bases. - Joerg Arndt, Jul 19 2012

Used PFGW (Fermat and Lucas, BLS) to determine (probable) primality of a(24)-a(26). - Robert Price, Jun 30 2013

a(27) > 10^5. - Robert Price, Jun 30 2013

a(29) > 2*10^5. - Robert Price, Dec 10 2013

a(31) > 3*10^5. - Tyler NeSmith, Dec 10 2020

LINKS

Table of n, a(n) for n=1..30.

MATHEMATICA

Do[ If[ PrimeQ[3^n + 4], Print[n] ], {n, 0, 3000} ]

PROG

(PARI) for(n=0, 10^5, if(ispseudoprime(3^n+4), print1(n, ", "))); /* Joerg Arndt, Jul 19 2012 */

(MAGMA) [n: n in [0..700] | IsPrime(3^n+4)]; // Vincenzo Librandi, Aug 25 2015

CROSSREFS

Cf. A102903 (corresponding primes).

Sequence in context: A191127 A015898 A157217 * A215618 A189708 A127590

Adjacent sequences:  A058955 A058956 A058957 * A058959 A058960 A058961

KEYWORD

nonn,hard,more

AUTHOR

Robert G. Wilson v, Jan 13 2001

EXTENSIONS

Terms 4629 ... 14730 from Joerg Arndt, Jul 19 2012

0 added by Bruno Berselli, Oct 04 2012

a(24)-a(26) from Robert Price, Jun 30 2013

a(27)-a(28) from Robert Price, Dec 10 2013

a(29)-a(30) from Tyler NeSmith, Dec 10 2020

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 03:04 EDT 2021. Contains 348099 sequences. (Running on oeis4.)