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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5039 |
| 8 | 40305 |
| 9 | 362682 |
| 10 | 3626190 |
| 11 | 39881160 |
| 12 | 478490760 |
| 13 | 6219298800 |
| 14 | 87055051511 |
| 15 | 1305598835941 |
| 16 | 20885951018102 |
| 17 | 354999461960226 |
| 18 | 6388879812001704 |
| 19 | 121367620532150280 |
| 20 | 2426930566055020080 |
| 21 | 50956684690331669759 |
| 22 | 1120852238721212726609 |