login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A102945 Numbers n such that 10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 3
1, 3, 12, 267, 843, 6300, 37992, 54117, 121242, 121621 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (17*10^n+1)/9 is prime.

No more terms below 133000. [Serge Batalov, May 15 2010]

a(11) > 2*10^5. - Robert Price, Nov 16 2014

LINKS

Table of n, a(n) for n=1..10.

Makoto Kamada, Prime numbers of the form 188...889.

Index entries for primes involving repunits.

FORMULA

a(n) = A102031(n) + 1.

MAPLE

A102945:=n->`if`(isprime((17*10^n+1)/9), n, NULL): seq(A102945(n), n=1..10^3); # Wesley Ivan Hurt, Nov 16 2014

MATHEMATICA

Do[ If[ PrimeQ[(17*10^n + 1)/9], Print[n]], {n, 0, 10000}]

Select[Range[1000], PrimeQ[(17 10^# + 1) / 9] &] (* Vincenzo Librandi, Nov 17 2014 *)

PROG

(MAGMA) [n: n in [0..300] | IsPrime((17*10^n+1) div 9)]; // Vincenzo Librandi, Nov 17 2014

CROSSREFS

Cf. A002275, A102031.

Sequence in context: A321603 A297564 A280086 * A300532 A249940 A132515

Adjacent sequences:  A102942 A102943 A102944 * A102946 A102947 A102948

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 16 2004

EXTENSIONS

More PRP terms a(7)-a(10). Sieved with srsieve and tested with Prime95 by Serge Batalov, May 15 2010

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 November 19 16:06 EST 2019. Contains 329320 sequences. (Running on oeis4.)