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 | 0 |
| 2 | 5 |
| 3 | -5 |
| 4 | 15 |
| 5 | -25 |
| 6 | 55 |
| 7 | -105 |
| 8 | 215 |
| 9 | -425 |
| 10 | 855 |
| 11 | -1705 |
| 12 | 3415 |
| 13 | -6825 |
| 14 | 13655 |
| 15 | -27305 |
| 16 | 54615 |
| 17 | -109225 |
| 18 | 218455 |
| 19 | -436905 |
| 20 | 873815 |
| 21 | -1747625 |
| 22 | 3495255 |
| 23 | -6990505 |
| 24 | 13981015 |
| 25 | -27962025 |
| 26 | 55924055 |
| 27 | -111848105 |
| 28 | 223696215 |
| 29 | -447392425 |
| 30 | 894784855 |
| 31 | -1789569705 |
| 32 | 3579139415 |