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 | 2 |
| 3 | -5 |
| 4 | 12 |
| 5 | -17 |
| 6 | -62 |
| 7 | 677 |
| 8 | -2840 |
| 9 | -1451 |
| 10 | 119954 |
| 11 | -866857 |
| 12 | 472540 |
| 13 | 52538185 |
| 14 | -517302474 |
| 15 | 410579683 |
| 16 | 47022181040 |
| 17 | -542323525061 |
| 18 | 101360204230 |
| 19 | 74342770852033 |
| 20 | -905627986876452 |
| 21 | -1359339244442825 |
| 22 | 186336992053330034 |