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 | 1 |
| 3 | 4 |
| 4 | 16 |
| 5 | 70 |
| 6 | 280 |
| 7 | 1168 |
| 8 | 4672 |
| 9 | 18884 |
| 10 | 75632 |
| 11 | 303368 |
| 12 | 1213472 |
| 13 | 4858064 |
| 14 | 19432256 |
| 15 | 77743040 |
| 16 | 310975520 |
| 17 | 1243959873 |
| 18 | 4975839492 |
| 19 | 19903598208 |
| 20 | 79614392832 |
| 21 | 318458493192 |
| 22 | 1273834028832 |
| 23 | 5095339755744 |
| 24 | 20381359022976 |
| 25 | 81525450936496 |
| 26 | 326101803775384 |