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 | 0 |
| 1 | 1 |
| 2 | 8 |
| 3 | 54 |
| 4 | 384 |
| 5 | 3000 |
| 6 | 25920 |
| 7 | 246960 |
| 8 | 2580480 |
| 9 | 29393280 |
| 10 | 362880000 |
| 11 | 4829932800 |
| 12 | 68976230400 |
| 13 | 1052366515200 |
| 14 | 17086945075200 |
| 15 | 294226732800000 |
| 16 | 5356234211328000 |
| 17 | 102793666719744000 |
| 18 | 2074369080655872000 |
| 19 | 43913881247588352000 |
| 20 | 973160803270656000000 |
| 21 | 22531105497723863040000 |