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A061430
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Geometric mean of the digits is an integer: k-digit numbers such that the product of the digits is a number of the form m^k.
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6
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 14, 19, 20, 22, 28, 30, 33, 40, 41, 44, 49, 50, 55, 60, 66, 70, 77, 80, 82, 88, 90, 91, 94, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 118, 120, 124, 130, 139, 140, 142, 150, 160, 170, 180, 181, 188, 190, 193
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graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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LINKS
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EXAMPLE
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694 is a term as (6*9*4)^(1/3) = 6 is an integer.
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MATHEMATICA
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Select[Range[0, 200], IntegerQ[GeometricMean[IntegerDigits[#]]]&] (* Harvey P. Dale, Feb 15 2012 *)
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PROG
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(Haskell)
a061430 n = a061430_list !! (n-1)
a061430_list = filter g [0..] where
g u = round (fromIntegral p ** (1 / fromIntegral k)) ^ k == p where
(p, k) = h (1, 0) u
h (p, l) 0 = (p, l)
h (p, l) v = h (p * r, l + 1) v' where (v', r) = divMod v 10
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CROSSREFS
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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