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 | 5 |
| 3 | 28 |
| 4 | 165 |
| 5 | 1001 |
| 6 | 6188 |
| 7 | 38760 |
| 8 | 245157 |
| 9 | 1562275 |
| 10 | 10015005 |
| 11 | 64512240 |
| 12 | 417225900 |
| 13 | 2707475148 |
| 14 | 17620076360 |
| 15 | 114955808528 |
| 16 | 751616304549 |
| 17 | 4923689695575 |
| 18 | 32308782859535 |
| 19 | 212327989773900 |
| 20 | 1397281501935165 |
| 21 | 9206478467454345 |
| 22 | 60727722660586800 |
| 23 | 400978991944396320 |