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 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 38 |
| 6 | 730 |
| 7 | 20670 |
| 8 | 781578 |
| 9 | 37885204 |
| 10 | 2289786624 |
| 11 | 168879532980 |
| 12 | 14930452838620 |
| 13 | 1558773675667164 |
| 14 | 189751596502711412 |
| 15 | 26640166205940265342 |
| 16 | 4272887377701537747810 |
| 17 | 776487144927243427031040 |
| 18 | 158705790134274513564693472 |
| 19 | 36246543562488282624570636306 |