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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 8 |
| 6 | 44 |
| 7 | 209 |
| 8 | 924 |
| 9 | 3927 |
| 10 | 16303 |
| 11 | 66691 |
| 12 | 270181 |
| 13 | 1087371 |
| 14 | 4356131 |
| 15 | 17394026 |
| 16 | 69289961 |
| 17 | 275543036 |
| 18 | 1094352236 |
| 19 | 4342295396 |
| 20 | 17218070066 |
| 21 | 68239187876 |
| 22 | 270351828476 |
| 23 | 1070824260326 |
| 24 | 4240695090452 |
| 25 | 16792454677874 |
| 26 | 66492351226050 |
| 27 | 263285419856250 |
| 28 | 1042540731845950 |