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 | 8 |
| 3 | 30 |
| 4 | 96 |
| 5 | 270 |
| 6 | 720 |
| 7 | 1820 |
| 8 | 4480 |
| 9 | 10710 |
| 10 | 25200 |
| 11 | 58212 |
| 12 | 133056 |
| 13 | 300300 |
| 14 | 672672 |
| 15 | 1492920 |
| 16 | 3294720 |
| 17 | 7220070 |
| 18 | 15752880 |
| 19 | 34179860 |
| 20 | 73902400 |
| 21 | 159074916 |
| 22 | 341429088 |
| 23 | 730122120 |
| 24 | 1557593856 |
| 25 | 3312591100 |
| 26 | 7030805600 |
| 27 | 14883258600 |
| 28 | 31451414400 |