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 | 24 |
| 3 | 80 |
| 4 | 248 |
| 5 | 768 |
| 6 | 2360 |
| 7 | 7200 |
| 8 | 21848 |
| 9 | 66048 |
| 10 | 199160 |
| 11 | 599520 |
| 12 | 1802648 |
| 13 | 5416128 |
| 14 | 16264760 |
| 15 | 48827040 |
| 16 | 146546648 |
| 17 | 439771008 |
| 18 | 1319575160 |
| 19 | 3959249760 |
| 20 | 11878797848 |
| 21 | 35638490688 |
| 22 | 106919666360 |
| 23 | 320767387680 |
| 24 | 962318940248 |
| 25 | 2886990375168 |
| 26 | 8661038234360 |