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 | -4 |
| 4 | -23 |
| 5 | -171 |
| 6 | -1542 |
| 7 | -16241 |
| 8 | -194973 |
| 9 | -2622610 |
| 10 | -39027573 |
| 11 | -636225591 |
| 12 | -11272598680 |
| 13 | -215668335091 |
| 14 | -4431191311809 |
| 15 | -97316894892644 |
| 16 | -2275184746472827 |
| 17 | -56421527472282127 |
| 18 | -1479397224086870294 |
| 19 | -40897073524132164189 |
| 20 | -1188896226524012279617 |