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 | 30 |
| 3 | 128 |
| 4 | 486 |
| 5 | 1692 |
| 6 | 5512 |
| 7 | 17040 |
| 8 | 50496 |
| 9 | 144512 |
| 10 | 401664 |
| 11 | 1089024 |
| 12 | 2890240 |
| 13 | 7529472 |
| 14 | 19298304 |
| 15 | 48754688 |
| 16 | 121602048 |
| 17 | 299827200 |
| 18 | 731643904 |
| 19 | 1768685568 |
| 20 | 4239261696 |
| 21 | 10081796096 |
| 22 | 23805296640 |
| 23 | 55839817728 |
| 24 | 130187001856 |
| 25 | 301813727232 |
| 26 | 696036360192 |
| 27 | 1597358735360 |