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 | 8 |
| 2 | 48 |
| 3 | 240 |
| 4 | 1080 |
| 5 | 4512 |
| 6 | 17856 |
| 7 | 67776 |
| 8 | 248880 |
| 9 | 889600 |
| 10 | 3109376 |
| 11 | 10664448 |
| 12 | 35989248 |
| 13 | 119761920 |
| 14 | 393676800 |
| 15 | 1280157696 |
| 16 | 4122985728 |
| 17 | 13165099008 |
| 18 | 41713192960 |
| 19 | 131243970560 |
| 20 | 410315433984 |
| 21 | 1275348344832 |