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 | 4 |
| 3 | 15 |
| 4 | 48 |
| 5 | 145 |
| 6 | 420 |
| 7 | 1183 |
| 8 | 3264 |
| 9 | 8865 |
| 10 | 23780 |
| 11 | 63151 |
| 12 | 166320 |
| 13 | 434993 |
| 14 | 1130948 |
| 15 | 2925375 |
| 16 | 7533312 |
| 17 | 19323713 |
| 18 | 49395780 |
| 19 | 125877071 |
| 20 | 319888560 |
| 21 | 810893265 |
| 22 | 2050891876 |
| 23 | 5176349663 |
| 24 | 13040153280 |
| 25 | 32793453025 |
| 26 | 82337215012 |
| 27 | 206424991215 |