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 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 93 |
| 6 | 464 |
| 7 | 1915 |
| 8 | 6336 |
| 9 | 316224 |
| 10 | 2805257 |
| 11 | 23139584 |
| 12 | 91581111 |
| 13 | 3772979200 |
| 14 | 77178291200 |
| 15 | 1022362697389 |
| 16 | 12006689439744 |
| 17 | 52812321503747 |
| 18 | 4709633119830016 |
| 19 | 110533093583273984 |
| 20 | 1995008117795780625 |