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 | 1 |
| 2 | 57 |
| 3 | 1071 |
| 4 | 12279 |
| 5 | 106738 |
| 6 | 781458 |
| 7 | 5111986 |
| 8 | 30980370 |
| 9 | 178047831 |
| 10 | 985621119 |
| 11 | 5311715977 |
| 12 | 28075774881 |
| 13 | 146309927344 |
| 14 | 754544640000 |
| 15 | 3861338821620 |
| 16 | 19646614600164 |
| 17 | 99532074868285 |
| 18 | 502608221035605 |
| 19 | 2531829420822835 |
| 20 | 12730273358124315 |
| 21 | 63919766245452606 |