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 | 8 |
| 5 | -18 |
| 6 | 39 |
| 7 | -89 |
| 8 | 204 |
| 9 | -472 |
| 10 | 1110 |
| 11 | -2616 |
| 12 | 6231 |
| 13 | -14909 |
| 14 | 35861 |
| 15 | -86705 |
| 16 | 210364 |
| 17 | -512480 |
| 18 | 1252350 |
| 19 | -3069638 |
| 20 | 7544818 |
| 21 | -18589202 |
| 22 | 45907708 |
| 23 | -113608590 |
| 24 | 281698359 |
| 25 | -699748003 |
| 26 | 1741102844 |
| 27 | -4338995332 |
| 28 | 10828981851 |
| 29 | -27063384783 |
| 30 | 67722954114 |
| 31 | -169674183372 |
| 32 | 425590855116 |
| 33 | -1068654838488 |