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) |
|---|---|
| 19 | 1 |
| 20 | 20 |
| 21 | 210 |
| 22 | 1540 |
| 23 | 8855 |
| 24 | 42504 |
| 25 | 177100 |
| 26 | 657800 |
| 27 | 2220075 |
| 28 | 6906900 |
| 29 | 20030010 |
| 30 | 54627300 |
| 31 | 141120525 |
| 32 | 347373600 |
| 33 | 818809200 |
| 34 | 1855967520 |
| 35 | 4059928950 |
| 36 | 8597496600 |
| 37 | 17672631900 |
| 38 | 35345263800 |
| 39 | 68923264410 |
| 40 | 131282408400 |
| 41 | 244662670200 |
| 42 | 446775310800 |
| 43 | 800472431850 |