cp's OEIS Frontend

A257294 The first d decimal digits of the geometric mean of the digits of n, where d is the number of digits of n, without leading zeros.

%I A257294 #9 May 11 2015 21:01:38
%S A257294 0,1,2,3,4,5,6,7,8,9,0,10,14,17,20,22,24,26,28,30,0,14,20,24,28,31,34,
%T A257294 37,40,42,0,17,24,30,34,38,42,45,48,51,0,20,28,34,40,44,48,52,56,60,0,
%U A257294 22,31,38,44,50,54,59,63,67,0,24,34,42,48,54,60,64,69,73,0,26,37,45,52,59,64
%N A257294 The first d decimal digits of the geometric mean of the digits of n, where d is the number of digits of n, without leading zeros.
%C A257294 Since the geometric mean of the digits of any number is either 0 or between 1 and 9, "the first d digits" is equivalent to the integer part of this value multiplied by 10^(d-1), which leads to the given formula.
%C A257294 Motivated by sequence A257830.
%F A257294 a(n) = floor(A007954(n)^(1/A055642(n))*10^(A055642(n)-1))
%e A257294 For n = 11, a 2-digit number, the geometric mean of the digits is trivially 1, which is 1.000..., and the first two decimal digits are 10, so a(11) = 10. For n=12, geometric mean is sqrt(2) = 1.414..., so a(12) = 14. - _N. J. A. Sloane_, May 11 2015
%o A257294 (PARI) a(n)=sqrtn(prod(i=1, #n=digits(n), n[i]), #n)\10^(1-#n)
%Y A257294 Cf. A004428, A004429, A007954, A055642, A257830.
%K A257294 nonn,base
%O A257294 0,3
%A A257294 _M. F. Hasler_, May 10 2015