What is the formula for an arithmetic series? Geometric series? Arithmetic sequence? Geometric series?
Here they are anyways:
Finding the nth term: An = A1 + d * (n - 1)
Sn = (n/2)*(A1 + An)
d is the common difference, An is the nth term, A1 is the first term.
For geometric series, there are many difference formulas to find the sum.
For infinite geometric series, those that don't have an end, (A1)/(n-1)
For those that do have an end, Sn = [A1(1-rn)]/(1-r)
r is the common ratio, A1 is the first term and n is the nth term.
To find the nth term:
An = ARn-1