Series and sequences equations

arithmetic sequence:

U_n = a + (n-1)d

a = first term

d = common difference

geometric sequence:

U_ⁿ = ar^n-1

a = first term

r = common ratio

arithmetic series:

S_n = ½ n(a+l) = ½ n [2a + (n-1) d]

geometric series:

S_n = a(1-rⁿ) / 1-r

Sum of geometric sequence to infinity:

A/1 -r