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 | 6 |
| 2 | 28 |
| 3 | 132 |
| 4 | 640 |
| 5 | 3156 |
| 6 | 15688 |
| 7 | 78252 |
| 8 | 390880 |
| 9 | 1953636 |
| 10 | 9766648 |
| 11 | 48830172 |
| 12 | 244144720 |
| 13 | 1220711316 |
| 14 | 6103532008 |
| 15 | 30517610892 |
| 16 | 152587956160 |
| 17 | 762939584196 |
| 18 | 3814697527768 |
| 19 | 19073486852412 |
| 20 | 95367432689200 |
| 21 | 476837160300276 |