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 | 0 |
| 2 | 1 |
| 3 | -2 |
| 4 | 9 |
| 5 | -44 |
| 6 | 265 |
| 7 | -1854 |
| 8 | 14833 |
| 9 | -133496 |
| 10 | 1334961 |
| 11 | -14684570 |
| 12 | 176214841 |
| 13 | -2290792932 |
| 14 | 32071101049 |
| 15 | -481066515734 |
| 16 | 7697064251745 |
| 17 | -130850092279664 |
| 18 | 2355301661033953 |
| 19 | -44750731559645106 |
| 20 | 895014631192902121 |
| 21 | -18795307255050944540 |
| 22 | 413496759611120779881 |