

A056716


Numbers n such that 6*10^n1 is prime.


4



0, 1, 2, 4, 5, 7, 10, 13, 22, 23, 28, 34, 40, 61, 73, 361, 490, 613, 1624, 2000, 2994, 4301, 4332, 18668, 32544, 34936, 267598, 270658, 293134, 319889, 414508
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OFFSET

1,3


COMMENTS

Also numbers n such that 5*10^n + 9*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.


LINKS

Table of n, a(n) for n=1..31.
Makoto Kamada, Prime numbers of the form 599...99.
Index entries for primes involving repunits


MATHEMATICA

Do[ If[ PrimeQ[ 6*10^n  1], Print[n]], {n, 0, 5000}]


PROG

(PARI) is(n)=ispseudoprime(6*10^n1) \\ Charles R Greathouse IV, Feb 20 2017


CROSSREFS

Cf. A056805 (6*10^n+1 is prime).
Sequence in context: A211523 A340246 A062463 * A223729 A190235 A023181
Adjacent sequences: A056713 A056714 A056715 * A056717 A056718 A056719


KEYWORD

hard,nonn,more


AUTHOR

Robert G. Wilson v, Aug 11 2000


EXTENSIONS

More terms from Hugo Pfoertner, Feb 12 2004
3 more terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 30 2007
a(27)a(31) from Kamada data by Robert Price, Oct 19 2014
Outdated comment deleted by Harvey P. Dale, Mar 01 2020


STATUS

approved



