# Boards with No All-Black Line Indicative time limit: 0.5 seconds. Memory limit: 8 MiB. Recalibrate as twice the slowest standard median in the target environment, rounded up to 0.5 seconds. See the [environment](../../../docs/评测环境与性能.md). ## Story A princess living on a mountaintop finds ordinary tic-tac-toe too small. On a larger board, she requires a white cell in every row, every column, and both long diagonals. Count the boards she can use. ## Formal Problem Statement Color every cell of an $n\times n$ board black or white. Every row, every column, the main diagonal, and the opposite diagonal must contain at least one white cell. The main diagonal consists of $(i,i)$ , and the opposite diagonal consists of $(i,n+1-i)$ , for $1\le i\le n$ . Only these two length-$n$ diagonals are checked. Board positions are distinguished: rotations and reflections are counted separately. For each $n=0,1,\ldots,20$ , find the number of boards modulo $P=10^9+7$ . The empty board has one coloring by convention. ![All five valid two-by-two boards](assets/example.svg) For $n=2$ , the five valid boards are the all-white board and the four boards with exactly one black cell. W means white and B means black. ## Input Format There is no input. ## Output Format Print 21 lines, giving the answers for $n=0$ through $n=20$ , in order. ## Sample 1 ### Input ```text ``` ### Output ```text 1 1 5 230 38154 23837323 867090702 313119612 923973197 462403141 840792457 982585751 463056058 199254391 8125702 241056829 669505845 625652964 167694588 415136241 104359615 ``` ## Constraints and Scoring There is no variable input. All 21 answers must be printed. Specification adjustment by Codex (GPT-6), recorded as a redesign: the whole-process memory limit is 8 MiB to accommodate the reference Windows runtime overhead. The input domain and counting or queue rules are unchanged. | Score | Additional constraints | | --- | --- | | 100% | None | There is one formal empty input file worth 100%. See the [test recipes](tests/README.md).