cp's OEIS Frontend

A061430 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.

%I A061430 #11 Jan 13 2014 12:39:26
%S A061430 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,
%T A061430 66,70,77,80,82,88,90,91,94,99,100,101,102,103,104,105,106,107,108,
%U A061430 109,110,111,118,120,124,130,139,140,142,150,160,170,180,181,188,190,193
%N A061430 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.
%H A061430 T. D. Noe, <a href="/A061430/b061430.txt">Table of n, a(n) for n=1..5000</a>
%e A061430 694 is a term as (6*9*4)^(1/3) = 6 is an integer.
%t A061430 Select[Range[0,200],IntegerQ[GeometricMean[IntegerDigits[#]]]&] (* _Harvey P. Dale_, Feb 15 2012 *)
%o A061430 (Haskell)
%o A061430 a061430 n = a061430_list !! (n-1)
%o A061430 a061430_list = filter g [0..] where
%o A061430    g u = round (fromIntegral p ** (1 / fromIntegral k)) ^ k == p where
%o A061430          (p, k) = h (1, 0) u
%o A061430          h (p, l) 0 = (p, l)
%o A061430          h (p, l) v = h (p * r, l + 1) v' where (v', r) = divMod v 10
%o A061430 -- _Reinhard Zumkeller_, Jan 13 2014
%Y A061430 Cf. A061426, A061427, A061428.
%K A061430 nonn,base,easy,nice
%O A061430 1,3
%A A061430 _Amarnath Murthy_, May 03 2001
%E A061430 More terms from _Naohiro Nomoto_, May 11 2001