Question 829363
This is surely an exponential growth.  Pick your base, either e or 10, or whatever you like; and try to fit to {{{y=a*b^(kx)}}}.
Use x as the index for your domain of Natural Numbers.  


The exponential equation can be put into a linear form:
{{{log((y))=log((a*b^(kx)))}}}
{{{log((y))=log((a))+kx*log((b))}}}---as a linear equation.
Recognize that log(b) for your chosen base of b will be 1.
{{{log((y))=log((a))+kx}}}
{{{highlight_green(log((y))=kx+log((a)))}}}
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Your function NOW is log(y) for the vertical component and x for the horizontal component.  This is an equation for a line, which your actual data may likely fit well.  The slope is k, and the vertical axis intercept is log(a).


Now knowing k and log((a)), your next value for x should be 6.  Use this to determine log((y)), and then find y.