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 | 3 |
| 2 | 12 |
| 3 | 60 |
| 4 | 396 |
| 5 | 3240 |
| 6 | 30960 |
| 7 | 335160 |
| 8 | 4072320 |
| 9 | 54976320 |
| 10 | 815119200 |
| 11 | 13152585600 |
| 12 | 229441766400 |
| 13 | 4303027048320 |
| 14 | 86318858545920 |
| 15 | 1843929831744000 |
| 16 | 41786821607731200 |
| 17 | 1001231951502182400 |
| 18 | 25288602517469491200 |
| 19 | 671488122628741017600 |