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 | 8 |
| 3 | -20 |
| 4 | 50 |
| 5 | -124 |
| 6 | 308 |
| 7 | -764 |
| 8 | 1896 |
| 9 | -4704 |
| 10 | 11672 |
| 11 | -28960 |
| 12 | 71856 |
| 13 | -178288 |
| 14 | 442368 |
| 15 | -1097600 |
| 16 | 2723360 |
| 17 | -6757184 |
| 18 | 16765888 |
| 19 | -41599424 |
| 20 | 103216256 |
| 21 | -256099584 |
| 22 | 635432832 |
| 23 | -1576632320 |
| 24 | 3911931136 |
| 25 | -9706261248 |
| 26 | 24083120128 |
| 27 | -59754900480 |
| 28 | 148263518720 |
| 29 | -367870598144 |