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 | 5 |
| 6 | 26 |
| 7 | 126 |
| 8 | 624 |
| 9 | 3193 |
| 10 | 17119 |
| 11 | 96668 |
| 12 | 576104 |
| 13 | 3621982 |
| 14 | 23980620 |
| 15 | 166805068 |
| 16 | 1215842905 |
| 17 | 9263445775 |
| 18 | 73599067250 |
| 19 | 608471202527 |
| 20 | 5224252803246 |
| 21 | 46499854580107 |
| 22 | 428369819029085 |
| 23 | 4078345518655015 |
| 24 | 40073659206668916 |
| 25 | 405885206895408576 |
| 26 | 4232705116291188276 |