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 | 18 |
| 5 | 55 |
| 6 | 174 |
| 7 | 566 |
| 8 | 1868 |
| 9 | 6237 |
| 10 | 21050 |
| 11 | 71666 |
| 12 | 245696 |
| 13 | 847317 |
| 14 | 2937116 |
| 15 | 10226574 |
| 16 | 35746292 |
| 17 | 125380257 |
| 18 | 441125966 |
| 19 | 1556301578 |
| 20 | 18155586993 |