This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -4 |
| 2 | 4 |
| 3 | 16 |
| 4 | 52 |
| 5 | 112 |
| 6 | -48 |
| 7 | -1984 |
| 8 | -11212 |
| 9 | -33360 |
| 10 | 6224 |
| 11 | 713536 |
| 12 | 4441872 |
| 13 | 13004480 |
| 14 | -17374656 |
| 15 | -432012032 |
| 16 | -2525831628 |
| 17 | -6454496208 |
| 18 | 21147389392 |
| 19 | 326358047552 |
| 20 | 1794285832464 |
| 21 | 4124461926592 |
| 22 | -19727734694848 |
| 23 | -263598020446976 |
| 24 | -1416694290412784 |
| 25 | -3151402998261312 |