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 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 5 |
| 5 | 48 |
| 6 | 252 |
| 7 | 1832 |
| 8 | 14625 |
| 9 | 132080 |
| 10 | 1323168 |
| 11 | 14576076 |
| 12 | 175108661 |
| 13 | 2278429216 |
| 14 | 31920719820 |
| 15 | 479088848976 |
| 16 | 7669098865441 |
| 17 | 130426934203296 |
| 18 | 2348478878321248 |
| 19 | 44633950190867220 |
| 20 | 892899715052136645 |