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A088266
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Smallest number that yields a prime when concatenated with A088265(k) for all k <= n.
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2
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2, 3, 3, 189, 210, 31296, 105441, 105441, 46814571, 665216481, 111581348556, 1199096907504
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OFFSET
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1,1
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COMMENTS
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a(n) == 0 (mod 3) for n > 1.
a(n) <> 4 (mod 7) and a(n) <> 9 (mod 11) for n > 2 (where <> means "not equal"). - M. F. Hasler, Oct 15 2012
Terms a(13) onward do not exist as at least one of the corresponding concatenations is always divisible by 7. - Max Alekseyev, Oct 14 2012
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LINKS
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EXAMPLE
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a(1) = 2 since 211 is prime.
a(4) = 189 since 18911, 18913, 18917 and 18919 are all prime.
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PROG
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(PARI) A088266(n)=for(t=1, 9e9, for(k=1, n, isprime(t*10^((k+7)\4)+A088265(k))||next(2)); return(t)) \\ Only useful for n<9. - M. F. Hasler, Oct 15 2012
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CROSSREFS
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KEYWORD
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base,nonn,fini,full
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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