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 | 4 |
| 3 | -9 |
| 4 | 19 |
| 5 | -41 |
| 6 | 88 |
| 7 | -189 |
| 8 | 406 |
| 9 | -872 |
| 10 | 1873 |
| 11 | -4023 |
| 12 | 8641 |
| 13 | -18560 |
| 14 | 39865 |
| 15 | -85626 |
| 16 | 183916 |
| 17 | -395033 |
| 18 | 848491 |
| 19 | -1822473 |
| 20 | 3914488 |
| 21 | -8407925 |
| 22 | 18059374 |
| 23 | -38789712 |
| 24 | 83316385 |
| 25 | -178955183 |
| 26 | 384377665 |
| 27 | -825604416 |
| 28 | 1773314929 |
| 29 | -3808901426 |
| 30 | 8181135700 |
| 31 | -17572253481 |
| 32 | 37743426307 |
| 33 | -81069068969 |