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 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 75 |
| 5 | 541 |
| 6 | 4683 |
| 7 | 47293 |
| 8 | 545835 |
| 9 | 7087261 |
| 10 | 102247562 |
| 11 | 1622632551 |
| 12 | 28091567067 |
| 13 | 526858335797 |
| 14 | 10641342662135 |
| 15 | 230283183134017 |
| 16 | 5315654473869451 |
| 17 | 130370761261559229 |
| 18 | 3385534496252337939 |
| 19 | 92801582269262225397 |
| 20 | 2677687636903407184463 |
| 21 | 81124819758167172293305 |