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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 28 |
| 4 | 117 |
| 5 | 2760 |
| 6 | 11481 |
| 7 | 270468 |
| 8 | 1125037 |
| 9 | 26503120 |
| 10 | 110242161 |
| 11 | 2597035308 |
| 12 | 10802606757 |
| 13 | 254482957080 |
| 14 | 1058545220041 |
| 15 | 24936732758548 |
| 16 | 103726628957277 |
| 17 | 2443545327380640 |
| 18 | 10164151092593121 |
| 19 | 239442505350544188 |
| 20 | 995983080445168597 |
| 21 | 23462921979025949800 |