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) |
|---|---|
| 4 | 4 |
| 5 | 140 |
| 6 | 3000 |
| 7 | 54600 |
| 8 | 940800 |
| 9 | 16087680 |
| 10 | 279417600 |
| 11 | 4989600000 |
| 12 | 92207808000 |
| 13 | 1769511744000 |
| 14 | 35321737651200 |
| 15 | 733823266176000 |
| 16 | 15866448998400000 |
| 17 | 356873052856320000 |
| 18 | 8344427063132160000 |
| 19 | 202660737281114112000 |