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 | 3 |
| 2 | 24 |
| 3 | 171 |
| 4 | 1200 |
| 5 | 8403 |
| 6 | 58824 |
| 7 | 411771 |
| 8 | 2882400 |
| 9 | 20176803 |
| 10 | 141237624 |
| 11 | 988663371 |
| 12 | 6920643600 |
| 13 | 48444505203 |
| 14 | 339111536424 |
| 15 | 2373780754971 |
| 16 | 16616465284800 |
| 17 | 116315256993603 |
| 18 | 814206798955224 |
| 19 | 5699447592686571 |
| 20 | 39896133148806000 |