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 | 1 |
| 4 | -6 |
| 5 | 35 |
| 6 | -215 |
| 7 | 1414 |
| 8 | -9912 |
| 9 | 73044 |
| 10 | -552570 |
| 11 | 4102626 |
| 12 | -26654826 |
| 13 | 79506492 |
| 14 | 2154425364 |
| 15 | -73527421176 |
| 16 | 1708053626880 |
| 17 | -35961691589640 |
| 18 | 736338276883080 |
| 19 | -15067241745943680 |
| 20 | 312009998091705720 |
| 21 | -6579362641255341120 |
| 22 | 141704946709227843480 |