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 | -6 |
| 3 | 21 |
| 4 | -68 |
| 5 | 198 |
| 6 | -510 |
| 7 | 1248 |
| 8 | -2904 |
| 9 | 6393 |
| 10 | -13604 |
| 11 | 28044 |
| 12 | -55956 |
| 13 | 108982 |
| 14 | -207552 |
| 15 | 386622 |
| 16 | -707216 |
| 17 | 1271970 |
| 18 | -2250582 |
| 19 | 3925780 |
| 20 | -6757272 |
| 21 | 11483232 |
| 22 | -19290824 |
| 23 | 32057352 |
| 24 | -52722744 |
| 25 | 85884503 |
| 26 | -138644292 |
| 27 | 221885805 |
| 28 | -352241792 |
| 29 | 554892894 |