7. Given the sequence $\left\{a_{n}\right\}$ satisfies
$$
a_{1}=1, a_{n}+a_{n+1}=-n^{2} \text {. }
$$

then $a_{15}=$ $\qquad$
7. -104 .

Rewrite $a_{n}+a_{n+1}=-n^{2}$ as
$$
\left(a_{n}+\frac{n^{2}}{2}-\frac{n}{2}\right)+\left[a_{n+1}+\frac{(n+1)^{2}}{2}-\frac{n+1}{2}\right]=0 \text {. }
$$

Let $b_{n}=a_{n}+\frac{n^{2}}{2}-\frac{n}{2}$. Then
$$
b_{1}=1 \text {, and } b_{n+1}=-b_{n} \text {. }
$$

Therefore, $b_{2 k-1}=1, b_{2 k}=-1(k=1,2, \cdots)$.
Thus, $b_{15}=1$, which means
$$
a_{15}=1+\frac{15}{2}-\frac{15^{2}}{2}=-104 .
$$