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 | 4 |
| 2 | 56 |
| 3 | 604 |
| 4 | 5936 |
| 5 | 55924 |
| 6 | 515816 |
| 7 | 4704844 |
| 8 | 42656096 |
| 9 | 385467364 |
| 10 | 3477018776 |
| 11 | 31332231484 |
| 12 | 282185395856 |
| 13 | 2540645125204 |
| 14 | 22870688939336 |
| 15 | 205860614516524 |
| 16 | 1852867600961216 |
| 17 | 16676418760213444 |
| 18 | 150090820599733496 |
| 19 | 1350832644186663964 |
| 20 | 12157570091625288176 |
| 21 | 109418512294354156084 |