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 | 2 |
| 2 | 4 |
| 3 | 12 |
| 4 | 40 |
| 5 | 148 |
| 6 | 572 |
| 7 | 2248 |
| 8 | 8920 |
| 9 | 35536 |
| 10 | 141860 |
| 11 | 566880 |
| 12 | 2266400 |
| 13 | 9063372 |
| 14 | 36249044 |
| 15 | 144987304 |
| 16 | 579931488 |
| 17 | 2319690516 |
| 18 | 9278691224 |
| 19 | 37114623248 |
| 20 | 148458209744 |
| 21 | 593832272556 |
| 22 | 2375327957436 |
| 23 | 9501309564288 |
| 24 | 38005233726372 |
| 25 | 152020925844036 |