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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

Robert Israel, Table of n, a(n) for n = 1..999

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

Adjacent sequences:  A174333 A174334 A174335 * A174337 A174338 A174339

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 December 10 15:09 EST 2019. Contains 329896 sequences. (Running on oeis4.)