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 | 4 |
| 2 | 112 |
| 3 | 1980 |
| 4 | 29120 |
| 5 | 387600 |
| 6 | 4845456 |
| 7 | 58017960 |
| 8 | 673171200 |
| 9 | 7625605680 |
| 10 | 84766052800 |
| 11 | 927990034972 |
| 12 | 10032268963392 |
| 13 | 107317291572400 |
| 14 | 1137727464904800 |
| 15 | 11968670068362000 |
| 16 | 125062895892372480 |
| 17 | 1299098807032012272 |
| 18 | 13423997084049034560 |
| 19 | 138068403550647828400 |
| 20 | 1414126456884869728000 |