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 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 16 |
| 7 | 50 |
| 8 | 158 |
| 9 | 472 |
| 10 | 1406 |
| 11 | 4111 |
| 12 | 11998 |
| 13 | 34781 |
| 14 | 100660 |
| 15 | 290464 |
| 16 | 837137 |
| 17 | 2408914 |
| 18 | 6925100 |
| 19 | 19888057 |
| 20 | 57071610 |