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 | 2 |
| 4 | 7 |
| 5 | 35 |
| 6 | 198 |
| 7 | 1302 |
| 8 | 9843 |
| 9 | 84216 |
| 10 | 804738 |
| 11 | 8494460 |
| 12 | 98158213 |
| 13 | 1232430908 |
| 14 | 16706285646 |
| 15 | 243169268856 |
| 16 | 3782633071103 |
| 17 | 62623591954942 |
| 18 | 1099391947653437 |
| 19 | 20399828362013787 |
| 20 | 398929976857158503 |