Considering the Fibonacci sequence how does F with subscript 1+2+3+4+5 = 610?

F(1+2+3+4+5)  = F(15) = 610

BTW.......we can calculate any Fibonacci number with index "n" using this formula....

[Phiⁿ - (-Phi)^-n ] / √5   ....where Phi = [ 1 + √5 ] / 2

The odd thing about this "formula" is that it looks as though it should produce some irrational number........but it doesn't !!!!

Try the formula with n = 15 and see if it doesn't give you 610.......

I do not remember hearing about  this number phi before about a week ago and since then it must have been mentioned half a dozen times.  I guess I should try to slot it into my memory bank somewhere.

Good luck there.   LOL