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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 4 |
| 4 | -7 |
| 5 | 19 |
| 6 | -40 |
| 7 | 97 |
| 8 | -217 |
| 9 | 508 |
| 10 | -1159 |
| 11 | 2683 |
| 12 | -6160 |
| 13 | 14209 |
| 14 | -32689 |
| 15 | 75316 |
| 16 | -173383 |
| 17 | 399331 |
| 18 | -919480 |
| 19 | 2117473 |
| 20 | -4875913 |
| 21 | 11228332 |
| 22 | -25856071 |
| 23 | 59541067 |
| 24 | -137109280 |
| 25 | 315732481 |
| 26 | -727060321 |
| 27 | 1674257764 |
| 28 | -3855438727 |
| 29 | 8878212019 |
| 30 | -20444528200 |
| 31 | 47079164257 |
| 32 | -108412748857 |