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 | 118 |
| 6 | 714 |
| 7 | 5012 |
| 8 | 40164 |
| 9 | 361872 |
| 10 | 3621366 |
| 11 | 39854930 |
| 12 | 478427452 |
| 13 | 6221137644 |
| 14 | 87112280208 |
| 15 | 1306869108686 |
| 16 | 20912175669082 |
| 17 | 355537064658852 |
| 18 | 6400095163337508 |
| 19 | 121608318630457872 |
| 20 | 2432271817858395382 |
| 21 | 51079520016325649394 |
| 22 | 1123782363517325646716 |