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 | 13 |
| 3 | 43 |
| 4 | 192 |
| 5 | 1068 |
| 6 | 7080 |
| 7 | 54360 |
| 8 | 473760 |
| 9 | 4616640 |
| 10 | 49714560 |
| 11 | 586051200 |
| 12 | 7504358400 |
| 13 | 103703846400 |
| 14 | 1538074137600 |
| 15 | 24366332390400 |
| 16 | 410609751552000 |
| 17 | 7333437855744000 |
| 18 | 138362409529344000 |
| 19 | 2749819506610176000 |
| 20 | 57416487392968704000 |
| 21 | 1256593887223234560000 |