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OFFSET
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1,1
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COMMENT
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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 (noe(AT)sspectra.com), Nov 16 2006
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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.
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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 (noe(AT)sspectra.com), Nov 16 2006
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CROSSREFS
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Cf. A000043, A000668, A002957, A002959, A003307, A079363, A055558.
Sequence in context: A119728 A133327 A001361 this_sequence A060110 A113468 A039665
Adjacent sequences: A120374 A120375 A120376 this_sequence 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 (wkehowski(AT)cox.net), Jun 28 2006
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EXTENSIONS
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Corrected by T. D. Noe (noe(AT)sspectra.com), Nov 16 2006
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