A174336 a(n) = the smallest n-digit number with exactly 5 divisors, or 0 if no such number exists.

0, 16, 625, 2401, 14641, 130321, 1874161, 12117361, 104060401, 1026625681, 10098039121, 100469346961, 1036488922561, 10106606869921, 100091400875761, 1011133218419041, 10028029413722401, 100004631514837921, 1000534329357902641, 10002039828958828561

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