%N Smallest power of 4 with digit sum n, or 0 if no such number exists.
%C a(3k)=0. If any other zero terms are really nonzero, their value is greater than 4^31. - Larry Reeves (larryr(AT)acm.org), Dec 21 2002
%Y Cf. A069025.
%A _Amarnath Murthy_, Apr 02 2002
%E More terms from Larry Reeves (larryr(AT)acm.org), Dec 21 2002