A182674 a(n) = the largest n-digit number with exactly 7 divisors, a(n) = 0 if no such number exists.

0, 64, 729, 0, 15625, 117649, 4826809, 47045881, 887503681, 6321363049, 90458382169, 832972004929, 7212549413161, 88245939632761, 940299110504209, 9851127637605409, 96279097826745289, 982134461213542729, 9645655601478045241, 99601110118185722929

Offset

1,2

Comments

a(n) = the largest n-digit number of the form p^6 (p = prime), a(n) = 0 if no such number exists.

Links

Table of n, a(n) for n=1..20.

Formula

A000005(a(n)) = 7.

Mathematica

Table[p=Floor[10^(n/6)]; While[p^6>10^(n-1) && ! PrimeQ[p], p = NextPrime[p, -1]]; If[p^6>10^(n-1), p^6, 0], {n, 20}]

Crossrefs

Cf. A182673 (smallest n-digit number with exactly 7 divisors).

Sequence in context: A008513 A321830 A182673 * A351194 A048392 A274219

Adjacent sequences: A182671 A182672 A182673 * A182675 A182676 A182677

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 27 2010

Status

approved