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 | 0 |
| 1 | 1 |
| 2 | 20 |
| 3 | 189 |
| 4 | 1356 |
| 5 | 8426 |
| 6 | 47944 |
| 7 | 257085 |
| 8 | 1321036 |
| 9 | 6574190 |
| 10 | 31911320 |
| 11 | 151841906 |
| 12 | 710828600 |
| 13 | 3282862644 |
| 14 | 14988894992 |
| 15 | 67769474077 |
| 16 | 303823057164 |
| 17 | 1352059744070 |
| 18 | 5977826290936 |
| 19 | 26277396651558 |
| 20 | 114916296684008 |
| 21 | 500229317398156 |
| 22 | 2168403190878960 |
| 23 | 9364025672275634 |