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A182680
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a(n) = the largest n-digit number with exactly 10 divisors, a(n) = 0 if no such number exists.
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1
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0, 80, 976, 9904, 99952, 999952, 9999952, 99999824, 999999536, 9999999824, 99999999536, 999999999567, 9999999999963, 99999999999728, 999999999999856, 9999999999998896, 99999999999999824, 999999999999999952, 9999999999999999856, 99999999999999999568
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OFFSET
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1,2
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COMMENTS
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a(n) = the largest n-digit number of the form p^9 or p^4*q (p, q distinct primes), a(n) = 0 if no such number exists.
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LINKS
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FORMULA
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MATHEMATICA
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Table[k=10^n-1; While[k>10^(n-1) && DivisorSigma[0, k] != 10, k--]; If[k==10^(n-1), k=0]; k, {n, 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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