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 | 5 |
| 2 | 55 |
| 3 | 360 |
| 4 | 3630 |
| 5 | 29820 |
| 6 | 321300 |
| 7 | 3225600 |
| 8 | 38808000 |
| 9 | 466300800 |
| 10 | 6360379200 |
| 11 | 89703936000 |
| 12 | 1389213504000 |
| 13 | 22565765376000 |
| 14 | 394272204480000 |
| 15 | 7248941973504000 |
| 16 | 141496402037760000 |
| 17 | 2901258659819520000 |
| 18 | 62617333274496000000 |
| 19 | 1414755114367795200000 |
| 20 | 33446554797269053440000 |