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) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 2 |
| 4 | 9 |
| 5 | 21 |
| 6 | 70 |
| 7 | 207 |
| 8 | 658 |
| 9 | 2059 |
| 10 | 6521 |
| 11 | 20602 |
| 12 | 65244 |
| 13 | 206608 |
| 14 | 654594 |
| 15 | 2073996 |
| 16 | 6571885 |
| 17 | 20824917 |
| 18 | 65991668 |
| 19 | 209121585 |
| 20 | 662691890 |
| 21 | 2100031249 |
| 22 | 6654888151 |
| 23 | 21089009696 |
| 24 | 66830061534 |
| 25 | 211781324846 |
| 26 | 671125181554 |
| 27 | 2126764718766 |