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 | -2 |
| 2 | 0 |
| 3 | -7 |
| 4 | -39 |
| 5 | -272 |
| 6 | -2457 |
| 7 | -26443 |
| 8 | -324675 |
| 9 | -4453439 |
| 10 | -67360840 |
| 11 | -1113125559 |
| 12 | -19949867987 |
| 13 | -385450438438 |
| 14 | -7987089578144 |
| 15 | -176710071650036 |
| 16 | -4158070097543962 |
| 17 | -103700987989612861 |
| 18 | -2732746882427265825 |
| 19 | -75882355625448093577 |
| 20 | -2214726801268428430553 |