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 | 1 |
| 3 | -1 |
| 4 | -3 |
| 5 | 19 |
| 6 | -65 |
| 7 | 181 |
| 8 | -419 |
| 9 | 755 |
| 10 | -749 |
| 11 | -1530 |
| 12 | 12255 |
| 13 | -47477 |
| 14 | 141065 |
| 15 | -343526 |
| 16 | 660941 |
| 17 | -770917 |
| 18 | -911369 |
| 19 | 9721976 |
| 20 | -40135713 |
| 21 | 124134772 |
| 22 | -313463842 |
| 23 | 631382751 |
| 24 | -824406065 |
| 25 | -492101356 |
| 26 | 8192253811 |
| 27 | -35948431288 |
| 28 | 115087580857 |
| 29 | -299576625051 |
| 30 | 627027769120 |
| 31 | -894734468883 |