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 | 3 |
| 2 | 6 |
| 3 | 20 |
| 4 | 72 |
| 5 | 276 |
| 6 | 1082 |
| 7 | 4356 |
| 8 | 17838 |
| 9 | 74100 |
| 10 | 311658 |
| 11 | 1325472 |
| 12 | 5677764 |
| 13 | 24530808 |
| 14 | 106487448 |
| 15 | 465271864 |
| 16 | 2039929380 |
| 17 | 8988480384 |
| 18 | 39714136328 |
| 19 | 176145529368 |
| 20 | 783061155762 |
| 21 | 3491535281916 |
| 22 | 15599247616188 |
| 23 | 69857485229124 |
| 24 | 313391213799998 |