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 | 21 |
| 2 | 420 |
| 3 | 8400 |
| 4 | 168000 |
| 5 | 3360000 |
| 6 | 67200000 |
| 7 | 1343999790 |
| 8 | 26879991600 |
| 9 | 537599748210 |
| 10 | 10751993288400 |
| 11 | 215039832252000 |
| 12 | 4300795974720000 |
| 13 | 86015906088000000 |
| 14 | 1720317853632043890 |
| 15 | 34406351710082593500 |