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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 2520 |
| 8 | 8400 |
| 9 | 28728 |
| 10 | 103050 |
| 11 | 390555 |
| 12 | 1566813 |
| 13 | 5994636 |
| 14 | 22318676 |
| 15 | 82337580 |
| 16 | 304360184 |
| 17 | 1134352752 |
| 18 | 4275368704 |
| 19 | 16107425628 |
| 20 | 60453074344 |
| 21 | 226179710040 |
| 22 | 845165016029 |
| 23 | 3159696003981 |
| 24 | 11832636916230 |
| 25 | 44346582492034 |
| 26 | 166184942954284 |