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 | -5 |
| 2 | 15 |
| 3 | -35 |
| 4 | 70 |
| 5 | -125 |
| 6 | 200 |
| 7 | -275 |
| 8 | 275 |
| 9 | 0 |
| 10 | -1000 |
| 11 | 3625 |
| 12 | -9500 |
| 13 | 21250 |
| 14 | -42500 |
| 15 | 76875 |
| 16 | -124375 |
| 17 | 171875 |
| 18 | -171875 |
| 19 | 0 |
| 20 | 621875 |
| 21 | -2250000 |
| 22 | 5890625 |
| 23 | -13171875 |
| 24 | 26343750 |
| 25 | -47656250 |
| 26 | 77109375 |
| 27 | -106562500 |
| 28 | 106562500 |
| 29 | 0 |