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A103105
Numbers n such that 9*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
0, 2, 4, 41, 53, 64, 197, 238, 784, 3914, 4436, 12538, 19036
OFFSET
1,2
COMMENTS
Also numbers n such that (88*10^n-61)/9 is prime.
a(14) > 10^5. - Robert Price, Nov 10 2015
FORMULA
a(n) = A101014(n-1) + 1, for n>1.
EXAMPLE
For n=0, (88*10^n-61)/9 = 3 which is prime.
MATHEMATICA
Do[ If[ PrimeQ[(88*10^n - 61)/9], Print[n]], {n, 0, 10000}]
PROG
(PARI) for(n=0, 1e3, if(ispseudoprime((88*10^n-61)/9), print1(n, ", "))) \\ Altug Alkan, Nov 11 2015
CROSSREFS
Sequence in context: A292700 A012676 A184245 * A018312 A009547 A215921
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(12)-a(13) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 by Robert Price, Nov 10 2015
STATUS
approved