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 | -3 |
| 4 | 6 |
| 5 | 30 |
| 6 | -720 |
| 7 | 9180 |
| 8 | -79020 |
| 9 | -283500 |
| 10 | 41886720 |
| 11 | -1580008680 |
| 12 | 44344341000 |
| 13 | -851982076440 |
| 14 | -5914076263200 |
| 15 | 1972181136416400 |
| 16 | -153108297672649200 |
| 17 | 8900721288190544400 |
| 18 | -403768420629168268800 |
| 19 | 9341444542413659205600 |
| 20 | 856476985107522346596000 |