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 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 30 |
| 7 | 100 |
| 8 | 380 |
| 9 | 1600 |
| 10 | 7400 |
| 11 | 37400 |
| 12 | 204600 |
| 13 | 1205600 |
| 14 | 7612000 |
| 15 | 51260000 |
| 16 | 366784000 |
| 17 | 2778820000 |
| 18 | 22222332000 |
| 19 | 187067320000 |
| 20 | 1653461480000 |
| 21 | 15310662400000 |
| 22 | 148217381840000 |
| 23 | 1497226615280000 |
| 24 | 15754506226800000 |
| 25 | 172407188412800000 |