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 | 1 |
| 2 | 3 |
| 3 | -2 |
| 4 | 19 |
| 5 | -54 |
| 6 | 222 |
| 7 | -804 |
| 8 | 3075 |
| 9 | -11630 |
| 10 | 44458 |
| 11 | -170268 |
| 12 | 654766 |
| 13 | -2524508 |
| 14 | 9758556 |
| 15 | -37802952 |
| 16 | 146724579 |
| 17 | -570450078 |
| 18 | 2221230066 |
| 19 | -8660901612 |
| 20 | 33811886394 |
| 21 | -132148736148 |
| 22 | 517012584036 |
| 23 | -2024632609272 |
| 24 | 7935337877454 |
| 25 | -31126450260204 |
| 26 | 122183595168612 |