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 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 50 |
| 5 | 94 |
| 6 | 2446 |
| 7 | -9024 |
| 8 | 297216 |
| 9 | -3183264 |
| 10 | 64191984 |
| 11 | -1041792192 |
| 12 | 22098943632 |
| 13 | -478805234064 |
| 14 | 11856288460272 |
| 15 | -308662348027008 |
| 16 | 8575865689645440 |
| 17 | -248582819381690880 |
| 18 | 7556655091130023680 |
| 19 | -240521346554744194560 |
| 20 | 8049494171497089265920 |
| 21 | -283469026458500121634560 |