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 | 2 |
| 3 | -4 |
| 4 | 6 |
| 5 | -12 |
| 6 | 20 |
| 7 | -36 |
| 8 | 64 |
| 9 | -112 |
| 10 | 200 |
| 11 | -352 |
| 12 | 624 |
| 13 | -1104 |
| 14 | 1952 |
| 15 | -3456 |
| 16 | 6112 |
| 17 | -10816 |
| 18 | 19136 |
| 19 | -33856 |
| 20 | 59904 |
| 21 | -105984 |
| 22 | 187520 |
| 23 | -331776 |
| 24 | 587008 |
| 25 | -1038592 |
| 26 | 1837568 |
| 27 | -3251200 |
| 28 | 5752320 |
| 29 | -10177536 |
| 30 | 18007040 |
| 31 | -31859712 |
| 32 | 56369152 |
| 33 | -99733504 |
| 34 | 176457728 |
| 35 | -312205312 |
| 36 | 552382464 |