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 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 52 |
| 5 | 255 |
| 6 | 4146 |
| 7 | 38766 |
| 8 | 688584 |
| 9 | 9685017 |
| 10 | 195875110 |
| 11 | 3655101703 |
| 12 | 84872077500 |
| 13 | 1955205893680 |
| 14 | 51896551499898 |
| 15 | 1412668946049315 |
| 16 | 42475968202854160 |
| 17 | 1328074354724554471 |
| 18 | 44778480417250291566 |
| 19 | 1577210136570598631318 |