A number j is a divisor of n if @c{$n \mathbin{\hbox{\code{\%}}} j = 0$} `n % j = 0'. The first step is to get a vector that identifies the divisors.
2: 30 2: [0, 0, 0, 2, ...] 1: [1, 1, 1, 0, ...]
1: [1, 2, 3, 4, ...] 1: 0 .
. .
30 RET v x 30 RET s 1 V M % 0 V M a = s 2
This vector has 1's marking divisors of 30 and 0's marking non-divisors.
The zeroth divisor function is just the total number of divisors. The first divisor function is the sum of the divisors.
1: 8 3: 8 2: 8 2: 8
2: [1, 2, 3, 4, ...] 1: [1, 2, 3, 0, ...] 1: 72
1: [1, 1, 1, 0, ...] . .
.
V R + r 1 r 2 V M * V R +
Once again, the last two steps just compute a dot product for which a simple * would have worked equally well.