A182647 a(n) = the largest n-digit number with exactly 5 divisors, a(n) = 0 if no such number exists.

0, 81, 625, 2401, 83521, 923521, 7890481, 88529281, 895745041, 9597924961, 96254442001, 988053892081, 9971252437441, 96840734511361, 999706081460641, 9892436613211441, 99510671548640641, 998005893107997601

Offset

1,2

Comments

a(n) = the largest n-digit number of the form p^4 (p = prime), a(n) = 0 if no such number exists.

Links

Table of n, a(n) for n=1..18.

Formula

A000005(a(n)) = 5.

Maple

A182647 := proc(n) a := 0 ; for i from 1 do p := ithprime(i)^4 ; if A055642(p) > n then return a ; elif A055642(p) = n then a := p; end if; end do: end proc:

Mathematica

Table[Prime[PrimePi[10^(n/4)]]^4, {n, 2, 50}]

Crossrefs

Cf. A030514, A174336.

Sequence in context: A206064 A359607 A016756 * A256590 A322240 A185856

Adjacent sequences: A182644 A182645 A182646 * A182648 A182649 A182650

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 27 2010

Extensions

Mathematica program by Zak Seidov, Nov 27 2010

Status

approved