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) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 16 |
| 4 | 105 |
| 5 | 768 |
| 6 | 6006 |
| 7 | 49152 |
| 8 | 415701 |
| 9 | 3604480 |
| 10 | 31870410 |
| 11 | 286261248 |
| 12 | 2604681690 |
| 13 | 23957864448 |
| 14 | 222399744300 |
| 15 | 2080911654912 |
| 16 | 19604537460045 |
| 17 | 185813170126848 |
| 18 | 1770558814528770 |
| 19 | 16951376923852800 |
| 20 | 162984598242674670 |