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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 12 |
| 6 | 49 |
| 7 | 210 |
| 8 | 927 |
| 9 | 4191 |
| 10 | 19305 |
| 11 | 90285 |
| 12 | 427570 |
| 13 | 2046324 |
| 14 | 9881862 |
| 15 | 48090824 |
| 16 | 235619133 |
| 17 | 1161257580 |
| 18 | 5753365015 |
| 19 | 28638093270 |
| 20 | 143148398085 |
| 21 | 718242481770 |
| 22 | 3616135914375 |
| 23 | 18263111515740 |
| 24 | 92500790125770 |
| 25 | 469737499557222 |
| 26 | 2391192703656054 |
| 27 | 12199557377107450 |