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 | 1 |
| 3 | 4 |
| 4 | 15 |
| 5 | 80 |
| 6 | 480 |
| 7 | 3444 |
| 8 | 27790 |
| 9 | 253504 |
| 10 | 2556792 |
| 11 | 28382880 |
| 12 | 343071168 |
| 13 | 4490999424 |
| 14 | 63253633872 |
| 15 | 954133373088 |
| 16 | 15343385194800 |
| 17 | 262060291958784 |
| 18 | 4737396899952384 |
| 19 | 90370907329842432 |
| 20 | 1814141041750834560 |
| 21 | 38229440785429201920 |
| 22 | 843786230514306621696 |