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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | -720 |
| 7 | 2520 |
| 8 | -6720 |
| 9 | 15120 |
| 10 | 1784160 |
| 11 | -39861360 |
| 12 | 478906560 |
| 13 | -4151192760 |
| 14 | 29059190160 |
| 15 | 43589505960 |
| 16 | -9531493695360 |
| 17 | 262248906060960 |
| 18 | -4781455284432960 |
| 19 | 68339552332044960 |
| 20 | -719390244156842880 |
| 21 | 105128808579670680 |
| 22 | 293382376643359246320 |