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 | 3720 |
| 8 | 17304 |
| 9 | 76110 |
| 10 | 329462 |
| 11 | 1441923 |
| 12 | 6487445 |
| 13 | 29555588 |
| 14 | 135025756 |
| 15 | 615260976 |
| 16 | 2791161792 |
| 17 | 12618600768 |
| 18 | 57008446080 |
| 19 | 257708989200 |
| 20 | 1166042944564 |
| 21 | 5279435858788 |
| 22 | 23908888017477 |
| 23 | 108262665958797 |
| 24 | 490132089640318 |
| 25 | 2218641353956314 |