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 | 10 |
| 5 | 48 |
| 6 | 276 |
| 7 | 1768 |
| 8 | 12552 |
| 9 | 97408 |
| 10 | 818704 |
| 11 | 7396384 |
| 12 | 71380640 |
| 13 | 732058880 |
| 14 | 7943068992 |
| 15 | 90833753728 |
| 16 | 1091134058624 |
| 17 | 13728139694080 |
| 18 | 180436251140352 |
| 19 | 2471790031618560 |