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 | 6 |
| 3 | 36 |
| 4 | 444 |
| 5 | 6540 |
| 6 | 119520 |
| 7 | 2593164 |
| 8 | 65233392 |
| 9 | 1867289868 |
| 10 | 59939612040 |
| 11 | 2132540249532 |
| 12 | 83293357351248 |
| 13 | 3543242182036284 |
| 14 | 163062595422642552 |
| 15 | 8071964230348189260 |
| 16 | 427682380939864204224 |
| 17 | 24149065480351703398572 |
| 18 | 1447640087400503974386504 |