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 | 9 |
| 2 | 72 |
| 3 | 576 |
| 4 | 5112 |
| 5 | 45432 |
| 6 | 408312 |
| 7 | 3669696 |
| 8 | 33022152 |
| 9 | 297153936 |
| 10 | 2674339992 |
| 11 | 24068651616 |
| 12 | 216617456232 |
| 13 | 1949553436392 |
| 14 | 17545977257832 |
| 15 | 157913762298336 |
| 16 | 1421223827662872 |
| 17 | 12791014151811912 |
| 18 | 115119127069153272 |
| 19 | 1036072140948039456 |
| 20 | 9324649265858015112 |