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 | 1 |
| 3 | -1 |
| 4 | -3 |
| 5 | 3 |
| 6 | 8 |
| 7 | -9 |
| 8 | -21 |
| 9 | 27 |
| 10 | 55 |
| 11 | -80 |
| 12 | -143 |
| 13 | 235 |
| 14 | 369 |
| 15 | -685 |
| 16 | -944 |
| 17 | 1983 |
| 18 | 2391 |
| 19 | -5705 |
| 20 | -5985 |
| 21 | 16320 |
| 22 | 14769 |
| 23 | -46441 |
| 24 | -35803 |
| 25 | 131507 |
| 26 | 84824 |
| 27 | -370665 |
| 28 | -194813 |
| 29 | 1040147 |
| 30 | 427767 |
| 31 | -2906448 |
| 32 | -874495 |
| 33 | 8088003 |
| 34 | 1564377 |
| 35 | -22416669 |
| 36 | -1971296 |
| 37 | 61883839 |
| 38 | -1016657 |
| 39 | -170165393 |
| 40 | 20507391 |
| 41 | 466069760 |