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 | 12 |
| 3 | 40 |
| 4 | 144 |
| 5 | 544 |
| 6 | 2112 |
| 7 | 8320 |
| 8 | 33024 |
| 9 | 131584 |
| 10 | 525312 |
| 11 | 2099200 |
| 12 | 8392704 |
| 13 | 33562624 |
| 14 | 134234112 |
| 15 | 536903680 |
| 16 | 2147549184 |
| 17 | 8590065664 |
| 18 | 34360000512 |
| 19 | 137439477760 |
| 20 | 549756862464 |
| 21 | 2199025352704 |
| 22 | 8796097216512 |
| 23 | 35184380477440 |
| 24 | 140737505132544 |
| 25 | 562949986975744 |