A099005 Numbers k such that 4*10^k + 6*R_k - 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 2, 3, 4, 6, 7, 8, 12, 23, 59, 75, 144, 204, 268, 760, 1216, 1430, 1506, 1509, 2804, 2924, 3201, 3305, 5753, 9268, 11279, 19677, 23414, 28627, 31362, 42299, 49119, 63747, 81767, 111443, 263720, 264791

Offset

1,2

Comments

Also numbers k such that (14*10^k - 11)/3 is a prime number.

a(38) > 3*10^5. - Robert Price, Mar 30 2015

Links

Table of n, a(n) for n=1..37.

Makoto Kamada, Prime numbers of the form 466...663.

Index entries for primes involving repunits.

Formula

a(n) = A101730(n) + 1.

Example

For n = 1, 2, 3, 4, 6, 7, 8 are members since 43, 463, 4663, 46663, 4666663, 46666663 and 466666663 are primes.

Mathematica

Do[ If[ PrimeQ[(14*10^n - 11)/3], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Dec 17 2004 *)

Crossrefs

Cf. A101730.

Sequence in context: A070525 A283112 A174099 * A336739 A257648 A096360

Adjacent sequences: A099002 A099003 A099004 * A099006 A099007 A099008

Keyword

more,nonn

Author

Julien Peter Benney (jpbenney(AT)ftml.net), Nov 07 2004

Extensions

a(15) - a(21) from Robert G. Wilson v, Dec 22 2004

a(22) - a(25) from Robert G. Wilson v, Jan 17 2005

a(26)-a(27) from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(28)-a(29) from Kamada data by Robert Price, Dec 08 2010

a(30)-a(32) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013

a(33)-a(34) from Kamada data by Robert Price, Mar 30 2015

a(35)-a(37) from Robert Price, May 31 2023

Status

approved