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 | 0 |
| 2 | -1 |
| 3 | -2 |
| 4 | 0 |
| 5 | 16 |
| 6 | 50 |
| 7 | -132 |
| 8 | -2184 |
| 9 | -9984 |
| 10 | 6912 |
| 11 | 341760 |
| 12 | 38544 |
| 13 | -47086272 |
| 14 | -702019344 |
| 15 | -6076389984 |
| 16 | -43980940800 |
| 17 | -656377887744 |
| 18 | -16782743357568 |
| 19 | -368775477229824 |
| 20 | -6770025717901056 |
| 21 | -118247220867640320 |
| 22 | -2271088046291742720 |
| 23 | -50203882870716579840 |