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A174336 a(n) = the smallest n-digit number with exactly 5 divisors, or 0 if no such number exists. 2
0, 16, 625, 2401, 14641, 130321, 1874161, 12117361, 104060401, 1026625681, 10098039121, 100469346961, 1036488922561, 10106606869921, 100091400875761, 1011133218419041, 10028029413722401, 100004631514837921, 1000534329357902641, 10002039828958828561 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(n) = the smallest n-digit number of the form p^4 (p = prime), a(n) = 0 if no such number exists.
LINKS
FORMULA
A000005(a(n)) = 5.
MAPLE
0, seq(nextprime(floor(10^((n-1)/4)))^4, n=2..30); # Robert Israel, Dec 05 2016
MATHEMATICA
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}]
PROG
(Magma) [0] cat [NextPrime(Floor(10^((n-1)/4)))^4: n in [2..25]]; // Vincenzo Librandi, Dec 06 2016
CROSSREFS
See A182647(n) - the largest n-digit number with exactly 5 divisors.
Sequence in context: A307943 A171210 A266129 * A135786 A016792 A077204
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 27 2010
EXTENSIONS
Extended by T. D. Noe, Nov 29 2010
STATUS
approved

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)