%N Smallest natural number k such that periodic part of 1/sqrt(k) is n (or 0 if no such number).
%C I believe a(n) = 0 will eventually occur (see A037207).
%C The smallest n such that A037207(n) = 0 is n = 101, so the smallest n such that a(n) = 0 is n = 101 as well. - _Jianing Song_, Feb 06 2019
%F a(n) = A037207(n)^2. - _Henry Bottomley_
%e 1/sqrt(20736) = 0.0069444444444444444444; a(4) = 20736.
%Y Cf. A037207.
%A _N. J. A. Sloane_
%E More terms from _Henry Bottomley_, Apr 28 2000