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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 12 |
| 6 | -14 |
| 7 | 135 |
| 8 | -276 |
| 9 | 1520 |
| 10 | -4056 |
| 11 | 17778 |
| 12 | -54392 |
| 13 | 213522 |
| 14 | -700362 |
| 15 | 2601674 |
| 16 | -8836812 |
| 17 | 31925046 |
| 18 | -110323056 |
| 19 | 393008712 |
| 20 | -1369533048 |
| 21 | 4844047090 |
| 22 | -16947396000 |
| 23 | 59723296431 |
| 24 | -209328634116 |
| 25 | 736260986208 |
| 26 | -2582605180212 |
| 27 | 9074182912884 |