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%I #10 Oct 05 2015 13:19:16
%S 0,64,729,0,15625,117649,1771561,24137569,148035889,2565726409,
%T 10779215329,128100283921,1061520150601,10942526586601,
%U 122978496247489,1014741853230169,10372926089038969,101513598260088169,1055229678769825441,10131553366728232321,101842394378135916961
%N a(n) = the smallest n-digit number with exactly 7 divisors, a(n) = 0 if no such number exists.
%C a(n) = the smallest n-digit number of the form p^6 (p = prime), a(n) = 0 if no such number exists.
%F A000005(a(n)) = 7.
%p A182673 := proc(n) for i from 1 do p := ithprime(i)^6 ; if A055642(p) > n then return 0 ; elif A055642(p) = n then return p; end if; end do: end proc:
%t Transpose[If[#[[1]]==#[[2]],{0,#[[2]]},#]&/@Partition[ Table[ NextPrime[ Surd[10^n,6]]^6,{n,0,40}],2,1]][[1]](* _Harvey P. Dale_, Oct 05 2015 *)
%Y Cf. A030516, A182674.
%K nonn,base
%O 1,2
%A _Jaroslav Krizek_, Nov 27 2010
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