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 | 6 |
| 2 | 42 |
| 3 | 228 |
| 4 | 1344 |
| 5 | 7800 |
| 6 | 46956 |
| 7 | 279972 |
| 8 | 1681008 |
| 9 | 10078164 |
| 10 | 60474120 |
| 11 | 362797116 |
| 12 | 2176832112 |
| 13 | 13060694088 |
| 14 | 78364444284 |
| 15 | 470185001040 |
| 16 | 2821111589856 |
| 17 | 16926659444832 |
| 18 | 101559966840108 |
| 19 | 609359740010604 |
| 20 | 3656158500550080 |