login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A227049 Numbers n such that (15^n + 4^n)/19 is prime. 2
3, 31, 157, 239, 1553, 5521, 25561 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are primes.

a(8) > 10^5.

LINKS

Table of n, a(n) for n=1..7.

MATHEMATICA

Select[ Prime[ Range[1, 100000] ], PrimeQ[ (15^# + 4^#)/19 ]& ]

PROG

(PARI) is(n)=ispseudoprime((15^n+4^n)/19) \\ Charles R Greathouse IV, Jun 06 2017

CROSSREFS

Cf. A057181, A128071, A128342, A213176, A224501, A221637.

Sequence in context: A087389 A294394 A064055 * A078604 A195603 A089286

Adjacent sequences:  A227046 A227047 A227048 * A227050 A227051 A227052

KEYWORD

hard,nonn,more

AUTHOR

Robert Price, Jun 29 2013

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 January 21 09:14 EST 2022. Contains 350475 sequences. (Running on oeis4.)