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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A178406 Numbers n such that 10^n - 41 is prime. 0
2, 6, 8, 12, 14, 47, 88, 130, 414, 1388, 1932, 4106, 4412, 12870, 22956, 23932, 27312, 35316, 37169, 43873, 150029 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The next term, if one exists, is >100000. - Robert Price, Apr 25 2011

a(22) > 2.5*10^5. - Robert Price, Apr 12 2015

LINKS

Table of n, a(n) for n=1..21.

Makoto Kamada, Near-repdigit numbers of the form AA...AABA.

Makoto Kamada, Prime numbers of the form 99...9959.

Index entries for primes involving repunits.

EXAMPLE

10^6 - 41 = 999959 which is a prime number.

MATHEMATICA

m=1000; For[n=1, n<m, If[PrimeQ[10^n-41], Print[n]]; n++ ]

PROG

(PARI) is(n)=ispseudoprime(10^n-41) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A108330, A108328.

Sequence in context: A120227 A276154 A138626 * A189515 A190344 A287000

Adjacent sequences:  A178403 A178404 A178405 * A178407 A178408 A178409

KEYWORD

more,nonn

AUTHOR

Robert Price, Dec 21 2010

EXTENSIONS

a(20)=43873 from Robert Price, Apr 25 2011

a(21) from Kamada data by Robert Price, Apr 12 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified September 26 05:09 EDT 2017. Contains 292502 sequences.