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) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | 5 |
| 4 | -15 |
| 5 | 54 |
| 6 | -226 |
| 7 | 1041 |
| 8 | -5045 |
| 9 | 25090 |
| 10 | -126674 |
| 11 | 646764 |
| 12 | -3335207 |
| 13 | 17359589 |
| 14 | -91138625 |
| 15 | 482237135 |
| 16 | -2569446532 |
| 17 | 13774698084 |
| 18 | -74245779493 |
| 19 | 402105384051 |
| 20 | -2187066640025 |
| 21 | 11941274232967 |
| 22 | -65425584835537 |
| 23 | 359598131529024 |
| 24 | -1982178299221646 |
| 25 | 10955208670488609 |
| 26 | -60696056311093958 |
| 27 | 337040131916813474 |