Minesweeper Squared
If you are unfamiliar with the rules of Minesweeper, here is a description:

Each of the redlabelled cells is either empty or contains a mine. All other cells are empty.

Each cell with a blue $1$ is adjacent to exactly one mine. Two cells are said to be adjacent if they share an edge or a corner. Thus, except at the border, every cell is adjacent to $8$ other cells.
Determine which of the redlabelled cells are safe, i.e., guaranteed to not contain a mine.
Input
An integer $n$ with $1 \leq n \leq 1\, 000$, the side length of the square. The image corresponds to $n = 6$.
It can be shown that there exists at least one valid placement of mines for each $n$.
Output
First print the number $m$ of safe cells. Then print a line with $m$ integers, the indices of the safe cells in increasing order. The cells are indexed clockwise from $1$ to $4n+4$, starting at the bottom left corner, as shown in the image.
Sample Input 1  Sample Output 1 

3 
8 1 3 5 7 9 11 13 15 
Sample Input 2  Sample Output 2 

1 
0 