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 | -1 |
| 4 | -2 |
| 5 | -4 |
| 6 | -10 |
| 7 | -29 |
| 8 | -90 |
| 9 | -290 |
| 10 | -960 |
| 11 | -3246 |
| 12 | -11164 |
| 13 | -38934 |
| 14 | -137358 |
| 15 | -489341 |
| 16 | -1757882 |
| 17 | -6360634 |
| 18 | -23160528 |
| 19 | -84802606 |
| 20 | -312041692 |
| 21 | -1153271984 |
| 22 | -4279311348 |
| 23 | -15935808866 |
| 24 | -59537435012 |
| 25 | -223099337404 |
| 26 | -838282693560 |
| 27 | -3157706225584 |
| 28 | -11922241414880 |