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OFFSET
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1,1
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COMMENTS
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See comments for A057472. Examined in base 12, all n must be even and all primes must be 1-primes. For example, 241 is 181 in base 12.
The n<1000 that yield primes are 2, 8, 248. - T. D. Noe, Nov 16 2006
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LINKS
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Table of n, a(n) for n=1..2.
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FORMULA
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a(n) = n-th number such that 2*11^k-1 that is prime for some k.
a(n) = 2*11^A120378(n)-1. [From R. J. Mathar, Mar 06 2010]
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EXAMPLE
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a(1)=241 since 2*11^2-1=241 is the first prime.
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MAPLE
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for w to 1 do for k from 1 to 2000 do n:=2*11^k-1; if isprime(n) then printf("%d, %d", k, n) fi od od;
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MATHEMATICA
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Select[2*11^Range[1000]-1, PrimeQ] - T. D. Noe, Nov 16 2006
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CROSSREFS
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Cf. A000043, A000668, A002957, A002959, A003307, A079363, A055558.
Sequence in context: A207286 A217998 A183891 * A171242 A060110 A113468
Adjacent sequences: A120374 A120375 A120376 * A120378 A120379 A120380
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KEYWORD
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nonn,bref
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AUTHOR
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Walter Kehowski, Jun 28 2006
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EXTENSIONS
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Corrected by T. D. Noe, Nov 16 2006
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STATUS
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approved
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