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 | 6 |
| 3 | 24 |
| 4 | 80 |
| 5 | 273 |
| 6 | 960 |
| 7 | 3336 |
| 8 | 11480 |
| 9 | 39648 |
| 10 | 136952 |
| 11 | 472416 |
| 12 | 1630164 |
| 13 | 5625480 |
| 14 | 19412736 |
| 15 | 66992016 |
| 16 | 231184800 |
| 17 | 797806152 |
| 18 | 2753187210 |
| 19 | 9501109380 |
| 20 | 32787848746 |