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!)
A101394 Numbers n such that 4*10^n+9 is prime. 1
0, 2, 4, 5, 8, 9, 28, 191, 196, 2038, 34414, 39266, 50579, 94286, 108412, 130480, 178091, 185355 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(19) > 2*10^5. - Robert Price, May 24 2015

LINKS

Table of n, a(n) for n=1..18.

Makoto Kamada, Prime numbers of the form 400...009.

Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.

FORMULA

a(n) = A101715(n-1) + 1.

EXAMPLE

n = 2, 4, 5, 8, 9 are members since 409, 40009, 400009, 400000009 and 4000000009 are all prime.

MATHEMATICA

Do[ If[ PrimeQ[4*10^n + 9], Print[n]], {n, 0, 10000}]

PROG

(PARI) is(n)=ispseudoprime(4*10^n+9) \\ Charles R Greathouse IV, Jun 12 2017

CROSSREFS

Cf. A088275, A056806, A101715.

Sequence in context: A227369 A092739 A277010 * A095031 A100598 A191535

Adjacent sequences:  A101391 A101392 A101393 * A101395 A101396 A101397

KEYWORD

nonn

AUTHOR

Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005

EXTENSIONS

a(10)=2038 from Joao da Silva (zxawyh66(AT)yahoo.com), Sep 30 2005

a(11)-a(12) from Kamada data by Robert Price, Dec 13 2010

Edited by Ray Chandler, Dec 23 2010

a(13)-a(18) from Robert Price, May 24 2015

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 26 02:14 EDT 2021. Contains 348256 sequences. (Running on oeis4.)