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A099017 Numbers k such that 4*10^k + 6*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k. 2
0, 1, 2, 6, 10, 12, 13, 22, 32, 46, 61, 68, 90, 110, 652, 1608, 1904, 2003, 3038, 3086, 9580, 9698, 10639, 14461 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers k such that (14*10^k + 1)/3 is prime.

a(25) > 2*10^5. - Robert Price, Jul 11 2015

LINKS

Table of n, a(n) for n=1..24.

Makoto Kamada, Prime numbers of the form 466...667.

Index entries for primes involving repunits.

FORMULA

a(n) = A101731(n-1) + 1, for n>1.

EXAMPLE

n = 1, 2, 6 are members since 47, 467, 4666667 are primes.

MATHEMATICA

Do[ If[ PrimeQ[(14*10^n + 1)/3], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Jan 17 2005 *)

CROSSREFS

Cf. A002275, A099005, A098959, A101731.

Sequence in context: A085258 A133520 A346299 * A298748 A139799 A214586

Adjacent sequences:  A099014 A099015 A099016 * A099018 A099019 A099020

KEYWORD

more,nonn

AUTHOR

Julien Peter Benney (jpbenney(AT)ftml.net), Nov 13 2004

EXTENSIONS

a(15)-a(22) from Robert G. Wilson v, Jan 17 2005

a(23)-a(24) from Kamada data by Robert Price, Dec 08 2010

Prepended a(1)=0 by Robert Price, Jul 11 2015

STATUS

approved

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Last modified August 8 17:55 EDT 2022. Contains 356016 sequences. (Running on oeis4.)