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A101393
Numbers k such that 3*10^k + R_k + 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
1
1, 2, 218, 692, 1805, 2207, 2873, 59135
OFFSET
1,2
COMMENTS
Also numbers k such that (28*10^k + 53)/9 is prime.
All except 1, 2 and 218 only probably prime. No others less than 10000.
FORMULA
a(n) = A101826(n) + 1.
EXAMPLE
n = 1, 2 are members since 37 and 317 are primes.
MATHEMATICA
Do[ If[ PrimeQ[(28*10^n+53)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
EXTENSIONS
a(8) from Kamada data by Robert Price, Dec 13 2010
STATUS
approved