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 | 1 |
| 3 | 1 |
| 4 | 0 |
| 5 | 5 |
| 6 | 30 |
| 7 | 77 |
| 8 | 192 |
| 9 | 879 |
| 10 | 3860 |
| 11 | 14102 |
| 12 | 52916 |
| 13 | 217295 |
| 14 | 896252 |
| 15 | 3631970 |
| 16 | 14862624 |
| 17 | 61811422 |
| 18 | 258539856 |
| 19 | 1084119347 |
| 20 | 4568946800 |
| 21 | 19360675922 |