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 | 6 |
| 4 | 43 |
| 5 | 321 |
| 6 | 2500 |
| 7 | 20096 |
| 8 | 165621 |
| 9 | 1392397 |
| 10 | 11896823 |
| 11 | 103014141 |
| 12 | 902035660 |
| 13 | 7974080834 |
| 14 | 71070247438 |
| 15 | 637937825112 |
| 16 | 5761970031357 |
| 17 | 52329993278856 |
| 18 | 477588786637264 |
| 19 | 4377832437503643 |
| 20 | 40288077072190109 |
| 21 | 372086539388626537 |
| 22 | 3447632819399550915 |