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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 36 |
| 6 | 108 |
| 7 | 324 |
| 8 | 1296 |
| 9 | 5184 |
| 10 | 20736 |
| 11 | 82944 |
| 12 | 331776 |
| 13 | 1327104 |
| 14 | 5308416 |
| 15 | 21233664 |
| 16 | 106168320 |
| 17 | 530841600 |
| 18 | 2654208000 |
| 19 | 13271040000 |
| 20 | 66355200000 |
| 21 | 331776000000 |
| 22 | 1658880000000 |
| 23 | 8294400000000 |
| 24 | 41472000000000 |
| 25 | 207360000000000 |
| 26 | 1036800000000000 |
| 27 | 5184000000000000 |