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 | 2 |
| 3 | -2 |
| 4 | 8 |
| 5 | 8 |
| 6 | 112 |
| 7 | 656 |
| 8 | 5504 |
| 9 | 49024 |
| 10 | 491264 |
| 11 | 5401856 |
| 12 | 64826368 |
| 13 | 842734592 |
| 14 | 11798300672 |
| 15 | 176974477312 |
| 16 | 2831591702528 |
| 17 | 48137058811904 |
| 18 | 866467058876416 |
| 19 | 16462874118127616 |
| 20 | 329257482363600896 |
| 21 | 6914407129633521664 |
| 22 | 152116956851941670912 |