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 | 1 |
| 3 | 9 |
| 4 | 50 |
| 5 | 234 |
| 6 | 1016 |
| 7 | 4256 |
| 8 | 17509 |
| 9 | 71349 |
| 10 | 289223 |
| 11 | 1168815 |
| 12 | 4714425 |
| 13 | 18991401 |
| 14 | 76434373 |
| 15 | 307411285 |
| 16 | 1235697666 |
| 17 | 4964876706 |
| 18 | 19940653388 |
| 19 | 80062371380 |
| 20 | 321361753426 |
| 21 | 1289589924226 |
| 22 | 5173842730758 |
| 23 | 20753408180790 |
| 24 | 83231772855896 |
| 25 | 333749033253560 |