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) |
|---|---|
| 1 | -1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 14 |
| 5 | 16 |
| 6 | -400 |
| 7 | -5312 |
| 8 | -33040 |
| 9 | 134400 |
| 10 | 7141632 |
| 11 | 104530944 |
| 12 | 438163968 |
| 13 | -19703033856 |
| 14 | -615381651456 |
| 15 | -8122606469120 |
| 16 | 54420468856832 |
| 17 | 5822016615940096 |
| 18 | 150504948558528512 |
| 19 | 1126972987747336192 |
| 20 | -72753308251479212032 |