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 | 4 |
| 2 | -13 |
| 3 | 49 |
| 4 | -181 |
| 5 | 676 |
| 6 | -2521 |
| 7 | 9409 |
| 8 | -35113 |
| 9 | 131044 |
| 10 | -489061 |
| 11 | 1825201 |
| 12 | -6811741 |
| 13 | 25421764 |
| 14 | -94875313 |
| 15 | 354079489 |
| 16 | -1321442641 |
| 17 | 4931691076 |
| 18 | -18405321661 |
| 19 | 68689595569 |
| 20 | -256353060613 |
| 21 | 956722646884 |
| 22 | -3570537526921 |
| 23 | 13325427460801 |
| 24 | -49731172316281 |
| 25 | 185599261804324 |