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 | 1 |
| 5 | 8 |
| 6 | 36 |
| 7 | 229 |
| 8 | 1625 |
| 9 | 13208 |
| 10 | 120288 |
| 11 | 1214673 |
| 12 | 13469897 |
| 13 | 162744944 |
| 14 | 2128047988 |
| 15 | 29943053061 |
| 16 | 451123462673 |
| 17 | 7245940789072 |
| 18 | 123604151490592 |
| 19 | 2231697509543361 |
| 20 | 42519034050101745 |
| 21 | 852495597142800376 |