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 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 85 |
| 5 | 430 |
| 6 | 2586 |
| 7 | 18109 |
| 8 | 144880 |
| 9 | 1303929 |
| 10 | 13039300 |
| 11 | 143432311 |
| 12 | 1721187744 |
| 13 | 22375440685 |
| 14 | 313256169604 |
| 15 | 4698842544075 |
| 16 | 75181480705216 |
| 17 | 1278085171988689 |
| 18 | 23005533095796420 |
| 19 | 437105128820131999 |
| 20 | 8742102576402640000 |
| 21 | 183584154104455440021 |
| 22 | 4038851390298019680484 |