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 | 7 |
| 3 | -19 |
| 4 | 51 |
| 5 | -135 |
| 6 | 359 |
| 7 | -955 |
| 8 | 2539 |
| 9 | -6751 |
| 10 | 17951 |
| 11 | -47731 |
| 12 | 126915 |
| 13 | -337463 |
| 14 | 897303 |
| 15 | -2385899 |
| 16 | 6344027 |
| 17 | -16868559 |
| 18 | 44852943 |
| 19 | -119262499 |
| 20 | 317115059 |
| 21 | -843198503 |
| 22 | 2242037063 |
| 23 | -5961502747 |
| 24 | 15851439563 |
| 25 | -42148455999 |
| 26 | 112071357055 |
| 27 | -297994049235 |
| 28 | 792356367523 |
| 29 | -2106849498391 |