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 | 4 |
| 3 | 12 |
| 4 | 60 |
| 5 | 300 |
| 6 | 1920 |
| 7 | 13440 |
| 8 | 109200 |
| 9 | 982800 |
| 10 | 9858240 |
| 11 | 108440640 |
| 12 | 1301952960 |
| 13 | 16925388480 |
| 14 | 236972736000 |
| 15 | 3554591040000 |
| 16 | 56873975558400 |
| 17 | 966857584492800 |
| 18 | 17403454164096000 |
| 19 | 330665629117824000 |
| 20 | 6613313252799052800 |
| 21 | 138879578308780108800 |
| 22 | 3055350750951750451200 |