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 | 2 |
| 2 | 12 |
| 3 | 114 |
| 4 | 1440 |
| 5 | 22368 |
| 6 | 409248 |
| 7 | 8585088 |
| 8 | 202733760 |
| 9 | 5317663680 |
| 10 | 153345634560 |
| 11 | 4821848409600 |
| 12 | 164211751261440 |
| 13 | 6022162697840640 |
| 14 | 236652023784960000 |
| 15 | 9921992082873223680 |
| 16 | 442138176056374548480 |
| 17 | 20869300232695599552000 |
| 18 | 1040210006521640127367680 |
| 19 | 54600929159270409876879360 |