%I #6 Mar 30 2012 19:00:24

%S 0,0,0,4096,0,531441,0,0,244140625,0,13841287201,0,3138428376721,

%T 23298085122481,582622237229761,2213314919066161,21914624432020321,

%U 353814783205469041,6582952005840035281,22563490300366186081

%N a(n) = the smallest n-digit number with exactly 13 divisors, a(n) = 0 if no such number exists.

%C a(n) = the smallest n-digit number of the form p^12 (p = prime), a(n) = 0 if no such number exists.

%F A000005(a(n)) = 13.

%F a(n) = A182686(n) for n <= 17.

%p A055642 := proc(n) max(1,ilog10(n)+1) ; end proc:

%p A182685 := proc(n) for i from 1 do p := ithprime(i)^12 ; if A055642(p) > n then return 0 ; elif A055642(p) = n then return p; end if; end do: end proc:

%Y Cf. A030631, A182686.

%K nonn,base

%O 1,4

%A _Jaroslav Krizek_, Nov 27 2010