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A102961 Numbers n such that 2*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 2, 7, 28, 73, 295, 494, 598, 2600, 3730, 7549, 15865 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (26*10^n-53)/9 is prime.

a(14) > 10^5. - Robert Price, Apr 18 2014

LINKS

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 288...883.

Index entries for primes involving repunits.

FORMULA

a(n) = A101970(n-1) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(26*10^n - 53)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101970.

Sequence in context: A294128 A099815 A123363 * A155581 A048504 A092465

Adjacent sequences:  A102958 A102959 A102960 * A102962 A102963 A102964

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 17 2004

EXTENSIONS

Addition of a(13) from Kamada data by Robert Price, Dec 13 2010

STATUS

approved

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Last modified March 21 10:09 EDT 2019. Contains 321368 sequences. (Running on oeis4.)