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) |
|---|---|
| 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 |