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 | 13 |
| 4 | -65 |
| 5 | 351 |
| 6 | -1989 |
| 7 | 11650 |
| 8 | -69900 |
| 9 | 427167 |
| 10 | -2648438 |
| 11 | 16612947 |
| 12 | -105215448 |
| 13 | 671760933 |
| 14 | -4318468133 |
| 15 | 27926126547 |
| 16 | -181520036139 |
| 17 | 1185220461607 |
| 18 | -7769787811032 |
| 19 | 51117085986564 |
| 20 | -337373170566291 |
| 21 | 2233091754693676 |
| 22 | -14819626688607761 |
| 23 | 98582852441111688 |