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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 125 |
| 6 | 755 |
| 7 | 5285 |
| 8 | 42286 |
| 9 | 380578 |
| 10 | 3805780 |
| 11 | 41863584 |
| 12 | 502363009 |
| 13 | 6530719126 |
| 14 | 91430067771 |
| 15 | 1371451016567 |
| 16 | 21943216265073 |
| 17 | 373034676506249 |
| 18 | 6714624177112491 |
| 19 | 127577859365137340 |
| 20 | 2551557187302746813 |