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 | 2 |
| 3 | 12 |
| 4 | 62 |
| 5 | 290 |
| 6 | 1292 |
| 7 | 5579 |
| 8 | 23606 |
| 9 | 98490 |
| 10 | 406862 |
| 11 | 1668689 |
| 12 | 6807704 |
| 13 | 27663441 |
| 14 | 112076057 |
| 15 | 453031502 |
| 16 | 1828018406 |
| 17 | 7366128866 |
| 18 | 29650536878 |
| 19 | 119249689265 |
| 20 | 479277846962 |
| 21 | 1925216817095 |
| 22 | 7729973578307 |
| 23 | 31025341749680 |
| 24 | 124486445913728 |
| 25 | 499362094315865 |