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A182685
a(n) = the smallest n-digit number with exactly 13 divisors, a(n) = 0 if no such number exists.
2
0, 0, 0, 4096, 0, 531441, 0, 0, 244140625, 0, 13841287201, 0, 3138428376721, 23298085122481, 582622237229761, 2213314919066161, 21914624432020321, 353814783205469041, 6582952005840035281, 22563490300366186081
OFFSET
1,4
COMMENTS
a(n) = the smallest n-digit number of the form p^12 (p = prime), a(n) = 0 if no such number exists.
FORMULA
A000005(a(n)) = 13.
a(n) = A182686(n) for n <= 17.
MAPLE
A055642 := proc(n) max(1, ilog10(n)+1) ; end proc:
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:
CROSSREFS
Sequence in context: A069439 A212935 A076154 * A182686 A369823 A176768
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 27 2010
STATUS
approved