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 | 17 |
| 5 | 273 |
| 6 | 4779 |
| 7 | 93532 |
| 8 | 2047730 |
| 9 | 49854795 |
| 10 | 1339872113 |
| 11 | 39462731031 |
| 12 | 1265248227869 |
| 13 | 43895994373580 |
| 14 | 1639148060192408 |
| 15 | 65568985769784897 |
| 16 | 2797922570156143597 |
| 17 | 126880981472647625557 |
| 18 | 6094210606862471240855 |
| 19 | 309087628703330034215088 |
| 20 | 16508178701980033054460042 |