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A174336
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a(n) = the smallest n-digit number with exactly 5 divisors, or 0 if no such number exists.
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2
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0, 16, 625, 2401, 14641, 130321, 1874161, 12117361, 104060401, 1026625681, 10098039121, 100469346961, 1036488922561, 10106606869921, 100091400875761, 1011133218419041, 10028029413722401, 100004631514837921, 1000534329357902641, 10002039828958828561
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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^4 (p = prime), a(n) = 0 if no such number exists.
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LINKS
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FORMULA
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MAPLE
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0, seq(nextprime(floor(10^((n-1)/4)))^4, n=2..30); # Robert Israel, Dec 05 2016
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MATHEMATICA
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Table[p=Ceiling[10^((n-1)/4)]; While[p^4<10^n && ! PrimeQ[p], p=NextPrime[p]]; If[p^4<10^n, p^4, 0], {n, 20}]
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PROG
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(Magma) [0] cat [NextPrime(Floor(10^((n-1)/4)))^4: n in [2..25]]; // Vincenzo Librandi, Dec 06 2016
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CROSSREFS
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See A182647(n) - the largest n-digit number with exactly 5 divisors.
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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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