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 | 0 |
| 3 | -5 |
| 4 | -14 |
| 5 | 56 |
| 6 | 736 |
| 7 | 1114 |
| 8 | -45156 |
| 9 | -428660 |
| 10 | 2004796 |
| 11 | 82797716 |
| 12 | 446153632 |
| 13 | -13593781928 |
| 14 | -276074700264 |
| 15 | 701782138576 |
| 16 | 107474258830096 |
| 17 | 1263010302870608 |
| 18 | -30208216250914352 |
| 19 | -1146149464640506928 |
| 20 | -2087509382334856224 |
| 21 | 703335832718961413056 |