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 | 4210 |
| 8 | 22782 |
| 9 | 117270 |
| 10 | 592121 |
| 11 | 2986213 |
| 12 | 15143820 |
| 13 | 77271338 |
| 14 | 395695883 |
| 15 | 2028110765 |
| 16 | 10390216994 |
| 17 | 53191249148 |
| 18 | 272166257616 |
| 19 | 1392326537756 |
| 20 | 7122760574924 |
| 21 | 36440848056190 |
| 22 | 186448403204159 |
| 23 | 953990833404741 |
| 24 | 4881270461542350 |