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 | 30 |
| 5 | 170 |
| 6 | 1320 |
| 7 | 11660 |
| 8 | 116600 |
| 9 | 1304600 |
| 10 | 15657400 |
| 11 | 230212400 |
| 12 | 3443176000 |
| 13 | 56312146000 |
| 14 | 1211416624000 |
| 15 | 23016735654000 |
| 16 | 460356735300000 |
| 17 | 12067735663300000 |
| 18 | 265756631234600000 |
| 19 | 6601271140642200000 |