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 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 12 |
| 5 | 74 |
| 6 | 538 |
| 7 | 4682 |
| 8 | 47280 |
| 9 | 545832 |
| 10 | 7087186 |
| 11 | 102247562 |
| 12 | 1622632020 |
| 13 | 28091567594 |
| 14 | 526858343698 |
| 15 | 10641342970366 |
| 16 | 230283190930560 |
| 17 | 5315654681981354 |
| 18 | 130370767028589528 |
| 19 | 3385534663256845322 |