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 | -2 |
| 3 | 7 |
| 4 | -27 |
| 5 | 115 |
| 6 | -510 |
| 7 | 2343 |
| 8 | -11029 |
| 9 | 52896 |
| 10 | -257457 |
| 11 | 1268098 |
| 12 | -6307546 |
| 13 | 31633044 |
| 14 | -159757597 |
| 15 | 811708539 |
| 16 | -4145882814 |
| 17 | 21273287952 |
| 18 | -109603172373 |
| 19 | 566748274099 |
| 20 | -2940175511195 |
| 21 | 15297961574259 |
| 22 | -79808998488751 |
| 23 | 417373462315834 |