

A111247


Numbers k such that (31*10^k  121) / 9 is prime.


0



2, 6, 8, 21, 66, 84, 86, 89, 93, 104, 170, 249, 273, 413, 824, 1392, 1589, 1679, 3125, 3185, 3482, 4089, 4772, 5138, 5738, 54761, 86364
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OFFSET

1,1


COMMENTS

Variant of repunit primes: each value is 3444...44431, with k2 4's.
a(28)> 2*10^5  Robert Price, Jun 07 2016


LINKS

Table of n, a(n) for n=1..27.
Makoto Kamada, Factorization of nearrepdigitrelated numbers.
Makoto Kamada, Search for 34w31.


EXAMPLE

6 is there because 3444431 is prime.
8 is there because 344444431 is prime.


MATHEMATICA

Select[Range[1200], PrimeQ[(31*10^#  121)/9]&] (* Vladimir Joseph Stephan Orlovsky, Feb 01 2012 *)


PROG

(PARI) is(n)=ispseudoprime((31*10^n  121)/9) \\ Charles R Greathouse IV, Jun 08 2016


CROSSREFS

Sequence in context: A290213 A058775 A103023 * A045656 A129342 A045654
Adjacent sequences: A111244 A111245 A111246 * A111248 A111249 A111250


KEYWORD

nonn,more


AUTHOR

Joao da Silva (zxawyh66(AT)yahoo.com), Oct 31 2005


EXTENSIONS

Edited by Don Reble, Nov 09 2005
a(16)  a(23) from Vladimir Joseph Stephan Orlovsky, Feb 01 2012
a(24)  a(27) from Robert Price, Jun 07 2016


STATUS

approved



