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 | -3 |
| 2 | 13 |
| 3 | -48 |
| 4 | 181 |
| 5 | -675 |
| 6 | 2521 |
| 7 | -9408 |
| 8 | 35113 |
| 9 | -131043 |
| 10 | 489061 |
| 11 | -1825200 |
| 12 | 6811741 |
| 13 | -25421763 |
| 14 | 94875313 |
| 15 | -354079488 |
| 16 | 1321442641 |
| 17 | -4931691075 |
| 18 | 18405321661 |
| 19 | -68689595568 |
| 20 | 256353060613 |
| 21 | -956722646883 |
| 22 | 3570537526921 |
| 23 | -13325427460800 |
| 24 | 49731172316281 |