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 | -2 |
| 2 | -4 |
| 3 | -4 |
| 4 | 24 |
| 5 | 236 |
| 6 | 1448 |
| 7 | 7640 |
| 8 | 37424 |
| 9 | 175436 |
| 10 | 798984 |
| 11 | 3565448 |
| 12 | 15672656 |
| 13 | 68098936 |
| 14 | 293196944 |
| 15 | 1253020976 |
| 16 | 5322318944 |
| 17 | 22491436556 |
| 18 | 94632958664 |
| 19 | 396682105256 |
| 20 | 1657418948624 |
| 21 | 6905368852136 |
| 22 | 28697991157424 |
| 23 | 119000162557136 |