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 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 9 |
| 4 | 28 |
| 5 | -15 |
| 6 | 306 |
| 7 | -1799 |
| 8 | 14904 |
| 9 | -133407 |
| 10 | 1335070 |
| 11 | -14684439 |
| 12 | 176214996 |
| 13 | -2290792751 |
| 14 | 32071101258 |
| 15 | -481066515495 |
| 16 | 7697064252016 |
| 17 | -130850092279359 |
| 18 | 2355301661034294 |
| 19 | -44750731559644727 |
| 20 | 895014631192902540 |
| 21 | -18795307255050944079 |