Question

What is the closed linear form for this sequence given a1 = 13 and an + 1 = an + 4?

Answer 1

I am assuming that the last part is

a(n+1) = a(n) + 4 so each term successive increases by 4

y = 4x + b

when x = 1, y = 13 so b = 9
y = 4x + 9

or

a(n) = 4n + 9