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 | -2 |
| 2 | 4 |
| 3 | -10 |
| 4 | 22 |
| 5 | -50 |
| 6 | 114 |
| 7 | -258 |
| 8 | 586 |
| 9 | -1330 |
| 10 | 3018 |
| 11 | -6850 |
| 12 | 15546 |
| 13 | -35282 |
| 14 | 80074 |
| 15 | -181730 |
| 16 | 412442 |
| 17 | -936050 |
| 18 | 2124394 |
| 19 | -4821378 |
| 20 | 10942266 |
| 21 | -24833810 |
| 22 | 56361098 |
| 23 | -127913250 |
| 24 | 290303066 |
| 25 | -658851762 |
| 26 | 1495284394 |
| 27 | -3393594050 |
| 28 | 7701866362 |
| 29 | -17479623250 |
| 30 | 39670544074 |
| 31 | -90033523298 |