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A182675
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a(n) = the smallest n-digit number with exactly 8 divisors, a(n) = 0 if no such number exists.
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1
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0, 24, 102, 1001, 10002, 100006, 1000002, 10000005, 100000006, 1000000003, 10000000001, 100000000006, 1000000000001, 10000000000001, 100000000000018, 1000000000000002, 10000000000000006, 100000000000000007, 1000000000000000001
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OFFSET
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1,2
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COMMENTS
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a(n) = the smallest n-digit number of the form p^7, p^3*q or p*q*r (p, q, r = distinct primes), a(n) = 0 if no such number exists.
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LINKS
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FORMULA
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a(n) = min {10^(n-1) <= k < 10^n : A000005(k)=8} if set is nonempty, else a(n) = 0.
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MAPLE
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with (numtheory):
a:= proc(n) local k;
if n<2 then 0
else for k from 10^(n-1) while tau(k)<>8
do od; k
fi
end:
seq (a(n), n=1..20);
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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