Question

The integer sequence a1, a2, a3, . . . , defined explicitly by
the formula an  5n for n ∈ Z+, can also be defined recursively
by
1) a1  5; and
2) an+1  an + 5, for n ≥ 1.
For the integer sequence b1, b2, b3, . . . , where bn 
n(n + 2) for all n ∈ Z+, we can also provide the recursive definition:
1)
b1  3; and
2)
bn+1  bn + 2n + 3, for n ≥ 1.
Give a recursive definition for each of the following integer
sequences c1, c2, c3, . . . , where for all n ∈ Z+ we have
a) csubn=  7n