Question 924657
Factor of 2, because "double" every three hours;


x hours,
y population at any x,
p initial population,
{{{highlight(y=p*2^(x/3))}}}.


for some constant k, x=3 means {{{k*3=1}}} period, {{{k=1/3}}}; so you want your exponent to be {{{x/3}}}.  This would be the only part needing great care.


Now, you can simply evaluate y for x=24 and p=n.
{{{y=n*2^(24/3)=n*2^8}}}