Please help, I'm understanding some parts of the sequence and then some parts are confusing. I remember doing these in algebra but they were much simpler. I thought I only had to plug & chug, but...

I need help with finding the sum of the first 5 terms of the sequence and they are defined recursively by:

$\displaystyle a_{1}=1; a_{2}= 2; \ a_{n}= \ a^2_{n-1} + a^2_{n-2}, \ n\geq3$;

The sum is 1 + 2 + 5 + 29 + 866 = 903.

I thought the way to do this was to replace n with the numbers 1 - 5:

$\displaystyle a_{1}= a^2_{2-1} + a^2_{2-2} = 1$ to get the sum, what I was wrong.

If I plug in '2' for the next sequence I don't get the right answer. How do I plug in the numbers and solve. I'm confused, please help! TIA...