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 | 118 |
| 6 | 674 |
| 7 | 4308 |
| 8 | 30062 |
| 9 | 225266 |
| 10 | 1791964 |
| 11 | 15009118 |
| 12 | 131566314 |
| 13 | 1201452248 |
| 14 | 11389283418 |
| 15 | 111761444078 |
| 16 | 1132680800640 |
| 17 | 11834071103246 |
| 18 | 127261591139010 |
| 19 | 1406778021294220 |
| 20 | 15967144849210158 |
| 21 | 185897394076705298 |