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 | -4 |
| 4 | 10 |
| 5 | 67 |
| 6 | -969 |
| 7 | 3341 |
| 8 | 86976 |
| 9 | -1988704 |
| 10 | 14144108 |
| 11 | 405611857 |
| 12 | -17544321563 |
| 13 | 287677263837 |
| 14 | 3595470378748 |
| 15 | -421298868094940 |
| 16 | 14476946230894114 |
| 17 | -112253861285434961 |
| 18 | -18711849695261432065 |
| 19 | 1354595712379990848137 |
| 20 | -44436925726445545236496 |