sequence+series

sequence

series

infinite

finite

list of numbers

when we add terms of sequence

arithmetic

increase by the same amount every term

nth term

\(a+(n-1)d\)

d=difference

arithmetic

number of terms*average of 1st and last term

first n numbers

\(\frac{n(n+1)}{2}\)

sum of first n odd integers \(n^2\)

geometric

common ratio between terms

\(n^{th}\) term

\(ar^{n-1}\)

geometric

sum: n. terms, first term a and common ratio r

\(\frac{a(r^n-1)}{r-1}\)

infinite geometric series

\(\frac{a}{1-r}\)