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

 

Logo

The October issue of the Notices of the Amer. Math. Soc. has an article about the OEIS.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A099413 Numbers n such that 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 2
0, 1, 2, 4, 10, 20, 26, 722, 1310, 3170, 28934, 66284, 67796 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (4*10^n+23)/9 is prime.

a(14) > 10^5. - Robert Price, Nov 26 2014

LINKS

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 44...447.

Index entries for primes involving repunits

FORMULA

a(n) = A056682(n-1) + 1. - Robert Price, Nov 26 2014

MATHEMATICA

Do[ If[ PrimeQ[ 4(10^n - 1)/9 + 3], Print[n]], {n, 5000}]

CROSSREFS

Cf. A002275, A056682.

Sequence in context: A083844 A026554 A259132 * A271624 A283090 A283143

Adjacent sequences:  A099410 A099411 A099412 * A099414 A099415 A099416

KEYWORD

nonn,hard,more

AUTHOR

Robert G. Wilson v, Oct 14 2004

EXTENSIONS

a(11)-a(13) from Robert Price, Nov 26 2014

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 24 22:27 EDT 2018. Contains 315360 sequences. (Running on oeis4.)