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 | 1 |
| 3 | 5 |
| 4 | 20 |
| 5 | 84 |
| 6 | 409 |
| 7 | 2365 |
| 8 | 16064 |
| 9 | 125664 |
| 10 | 1112073 |
| 11 | 10976173 |
| 12 | 119481284 |
| 13 | 1421542628 |
| 14 | 18348340113 |
| 15 | 255323504917 |
| 16 | 3809950976992 |
| 17 | 60683990530208 |
| 18 | 1027542662934897 |
| 19 | 18430998766219317 |
| 20 | 349096664728623316 |
| 21 | 6962409983976703316 |
| 22 | 145841989688186383337 |