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 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 48 |
| 6 | 140 |
| 7 | 408 |
| 8 | 1224 |
| 9 | 3640 |
| 10 | 10824 |
| 11 | 32192 |
| 12 | 96576 |
| 13 | 288912 |
| 14 | 864288 |
| 15 | 2585584 |
| 16 | 7735104 |
| 17 | 23205312 |
| 18 | 69551552 |
| 19 | 208461504 |
| 20 | 624806688 |
| 21 | 1872691488 |
| 22 | 5612903296 |
| 23 | 16838709888 |
| 24 | 50500659456 |
| 25 | 151455567744 |
| 26 | 454227600128 |
| 27 | 1362265877376 |