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 | 1 |
| 3 | -4 |
| 4 | 8 |
| 5 | -19 |
| 6 | 42 |
| 7 | -95 |
| 8 | 213 |
| 9 | -479 |
| 10 | 1076 |
| 11 | -2418 |
| 12 | 5433 |
| 13 | -12208 |
| 14 | 27431 |
| 15 | -61637 |
| 16 | 138497 |
| 17 | -311200 |
| 18 | 699260 |
| 19 | -1571223 |
| 20 | 3530506 |
| 21 | -7932975 |
| 22 | 17825233 |
| 23 | -40052935 |
| 24 | 89998128 |
| 25 | -202223958 |
| 26 | 454393109 |
| 27 | -1021012048 |
| 28 | 2294193247 |
| 29 | -5155005433 |
| 30 | 11583192065 |