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 | 2 |
| 3 | -4 |
| 4 | 5 |
| 5 | -10 |
| 6 | 14 |
| 7 | -28 |
| 8 | 42 |
| 9 | -84 |
| 10 | 132 |
| 11 | -264 |
| 12 | 429 |
| 13 | -858 |
| 14 | 1430 |
| 15 | -2860 |
| 16 | 4862 |
| 17 | -9724 |
| 18 | 16796 |
| 19 | -33592 |
| 20 | 58786 |
| 21 | -117572 |
| 22 | 208012 |
| 23 | -416024 |
| 24 | 742900 |
| 25 | -1485800 |
| 26 | 2674440 |
| 27 | -5348880 |
| 28 | 9694845 |
| 29 | -19389690 |
| 30 | 35357670 |
| 31 | -70715340 |
| 32 | 129644790 |
| 33 | -259289580 |
| 34 | 477638700 |
| 35 | -955277400 |
| 36 | 1767263190 |
| 37 | -3534526380 |