A103038 - OEIS

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A103038

Numbers n such that 6*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1

0, 1, 3, 4, 10, 22, 40, 54, 81, 84, 106, 193, 597, 681, 1363, 1876, 4024, 14163, 18733, 20842, 23728, 26419, 31450, 44694, 64767

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OFFSET

1,3

COMMENTS

Also numbers n such that (59*10^n-41)/9 is prime.

a(26) > 10^5. - Robert Price, Sep 11 2015

LINKS

Table of n, a(n) for n=1..25.

Makoto Kamada, Prime numbers of the form 655...551.

Index entries for primes involving repunits.

FORMULA

a(n) = A101531(n-1) + 1 for n>1.

MATHEMATICA

Do[ If[ PrimeQ[(59*10^n - 41)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101531.

Sequence in context: A109887 A200981 A266729 * A143108 A169790 A014009

Adjacent sequences: A103035 A103036 A103037 * A103039 A103040 A103041

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 18 2005

EXTENSIONS

a(18)-a(22) from Kamada data by Robert Price, Dec 14 2010

a(23)-a(24) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Inserted a(1)=0 by Robert Price, Sep 11 2015

a(25) from Robert Price, Sep 11 2015

STATUS

approved