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 | 4 |
| 2 | 16 |
| 3 | 54 |
| 4 | 176 |
| 5 | 564 |
| 6 | 1790 |
| 7 | 5646 |
| 8 | 17732 |
| 9 | 55512 |
| 10 | 173354 |
| 11 | 540258 |
| 12 | 1680848 |
| 13 | 5221740 |
| 14 | 16200758 |
| 15 | 50204790 |
| 16 | 155413724 |
| 17 | 480622848 |
| 18 | 1484980802 |
| 19 | 4584213642 |
| 20 | 14140323560 |
| 21 | 43583756436 |
| 22 | 134239102286 |
| 23 | 413179757214 |
| 24 | 1270924525556 |
| 25 | 3906925144104 |