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 | 4 |
| 2 | 12 |
| 3 | 60 |
| 4 | 240 |
| 5 | 1020 |
| 6 | 4020 |
| 7 | 16380 |
| 8 | 65280 |
| 9 | 262080 |
| 10 | 1047540 |
| 11 | 4194300 |
| 12 | 16772880 |
| 13 | 67108860 |
| 14 | 268419060 |
| 15 | 1073740740 |
| 16 | 4294901760 |
| 17 | 17179869180 |
| 18 | 68719210560 |
| 19 | 274877906940 |
| 20 | 1099510578960 |
| 21 | 4398046494660 |
| 22 | 17592181850100 |
| 23 | 70368744177660 |
| 24 | 281474959868160 |