

A103063


Numbers n such that 7*10^n + 6*R_n  5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



0, 1, 2, 6, 25, 69, 253, 300, 384, 434, 721, 822, 883, 2192, 2649, 3441, 3445, 8028, 11655
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OFFSET

1,3


COMMENTS

Also numbers n such that (23*10^n17)/3 is prime.
a(20) > 10^5.  Robert Price, Oct 22 2015


LINKS

Table of n, a(n) for n=1..19.
Makoto Kamada, Prime numbers of the form 766...661.
Index entries for primes involving repunits.


FORMULA

a(n) = A101147(n1) + 1, for n>1.


EXAMPLE

For n=0, (23*10^n  17)/3 = , which is prime.


MATHEMATICA

Do[ If[ PrimeQ[(23*10^n  17)/3], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101147.
Sequence in context: A173609 A294945 A073545 * A220191 A030228 A066317
Adjacent sequences: A103060 A103061 A103062 * A103064 A103065 A103066


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

a(19) from Kamada data by Robert Price, Dec 14 2010
a(1)=0 inserted by Robert Price, Oct 22 2015


STATUS

approved



