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 | 504 |
| 7 | 1902 |
| 8 | 6902 |
| 9 | 25231 |
| 10 | 95401 |
| 11 | 365116 |
| 12 | 1396948 |
| 13 | 5316192 |
| 14 | 20135712 |
| 15 | 76227216 |
| 16 | 288878956 |
| 17 | 1095937420 |
| 18 | 4159450913 |
| 19 | 15783649241 |
| 20 | 59878012558 |
| 21 | 227128287882 |
| 22 | 861543171080 |
| 23 | 3268198646496 |
| 24 | 12398132725784 |
| 25 | 47033439463906 |
| 26 | 178423731589482 |