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 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 56 |
| 6 | 318 |
| 7 | 2134 |
| 8 | 16430 |
| 9 | 142945 |
| 10 | 1386570 |
| 11 | 14836295 |
| 12 | 173584650 |
| 13 | 2204525052 |
| 14 | 30201993206 |
| 15 | 443969300123 |
| 16 | 6970318011936 |
| 17 | 116404310799339 |
| 18 | 2060356301148292 |
| 19 | 38528662831473069 |
| 20 | 759014657780019468 |