1. **State the problem:**
We are given a recurrence relation
$$q_n = n q_{n-1} + n^2 q_{n-2}$$
with initial conditions
$$q_0 = 1, q_1 = 1.$$
We want to find values of $q_n$ for $n = 2, 3, 4, 5$.
2. **Calculate $q_2$:**
Using the recurrence for $n=2$,
$$q_2 = 2 imes q_1 + 2^2 imes q_0 = 2 imes 1 + 4 imes 1 = 2 + 4 = 6.$$
3. **Calculate $q_3$:**
For $n=3$,
$$q_3 = 3 imes q_2 + 3^2 imes q_1 = 3 imes 6 + 9 imes 1 = 18 + 9 = 27.$$
4. **Calculate $q_4$:**
For $n=4$,
$$q_4 = 4 imes q_3 + 4^2 imes q_2 = 4 imes 27 + 16 imes 6 = 108 + 96 = 204.$$
5. **Calculate $q_5$:**
For $n=5$,
$$q_5 = 5 imes q_4 + 5^2 imes q_3 = 5 imes 204 + 25 imes 27 = 1020 + 675 = 1695.$$
**Final answers:**
$$q_2 = 6, \quad q_3 = 27, \quad q_4 = 204, \quad q_5 = 1695.$$
Recurrence Sequence
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