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 | 0 |
| 2 | 0 |
| 3 | -1 |
| 4 | 2 |
| 5 | -3 |
| 6 | 5 |
| 7 | -9 |
| 8 | 16 |
| 9 | -28 |
| 10 | 49 |
| 11 | -86 |
| 12 | 151 |
| 13 | -265 |
| 14 | 465 |
| 15 | -816 |
| 16 | 1432 |
| 17 | -2513 |
| 18 | 4410 |
| 19 | -7739 |
| 20 | 13581 |
| 21 | -23833 |
| 22 | 41824 |
| 23 | -73396 |
| 24 | 128801 |
| 25 | -226030 |
| 26 | 396655 |
| 27 | -696081 |
| 28 | 1221537 |
| 29 | -2143648 |
| 30 | 3761840 |
| 31 | -6601569 |
| 32 | 11584946 |
| 33 | -20330163 |
| 34 | 35676949 |
| 35 | -62608681 |
| 36 | 109870576 |
| 37 | -192809420 |
| 38 | 338356945 |
| 39 | -593775046 |
| 40 | 1042002567 |