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 | 1 |
| 2 | -2 |
| 3 | 1 |
| 4 | -4 |
| 5 | 29 |
| 6 | -244 |
| 7 | 1583 |
| 8 | -10368 |
| 9 | 124553 |
| 10 | -2029776 |
| 11 | 20127867 |
| 12 | -180343296 |
| 13 | 3978820221 |
| 14 | -75977108544 |
| 15 | 914656587063 |
| 16 | -15574206480384 |
| 17 | 370244721585681 |
| 18 | -8082505243732224 |
| 19 | 162968423791332339 |
| 20 | -3082360882836013056 |
| 21 | 82014901819948738629 |
| 22 | -2501342802748968883200 |
| 23 | 58311771938510122952559 |