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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | 2 |
| 5 | -5 |
| 6 | 13 |
| 7 | -33 |
| 8 | 80 |
| 9 | -184 |
| 10 | 402 |
| 11 | -840 |
| 12 | 1699 |
| 13 | -3382 |
| 14 | 6750 |
| 15 | -13716 |
| 16 | 28550 |
| 17 | -60587 |
| 18 | 129579 |
| 19 | -275915 |
| 20 | 579828 |
| 21 | -1197649 |
| 22 | 2431775 |
| 23 | -4870105 |
| 24 | 9672634 |
| 25 | -19173013 |
| 26 | 38151533 |
| 27 | -76521331 |
| 28 | 154941608 |
| 29 | -316399235 |
| 30 | 649807589 |
| 31 | -1337598675 |
| 32 | 2751021907 |
| 33 | -5640238583 |
| 34 | 11513062785 |
| 35 | -23389948481 |
| 36 | 47310801199 |
| 37 | -95345789479 |
| 38 | 191616365385 |