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 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 9 |
| 6 | 55 |
| 7 | 51 |
| 8 | 252 |
| 9 | 379 |
| 10 | 1491 |
| 11 | 1611 |
| 12 | 12236 |
| 13 | 10245 |
| 14 | 57057 |
| 15 | 121711 |
| 16 | 345888 |
| 17 | 474489 |
| 18 | 3589099 |
| 19 | 3397143 |
| 20 | 21983298 |
| 21 | 41570721 |
| 22 | 142617777 |
| 23 | 186027579 |
| 24 | 1476401628 |
| 25 | 1694455311 |
| 26 | 8146623393 |
| 27 | 15690140775 |