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 | 20 |
| 3 | 96 |
| 4 | 444 |
| 5 | 2000 |
| 6 | 8840 |
| 7 | 38528 |
| 8 | 166124 |
| 9 | 710256 |
| 10 | 3016056 |
| 11 | 12736064 |
| 12 | 53530840 |
| 13 | 224107936 |
| 14 | 935062544 |
| 15 | 3890018816 |
| 16 | 16141765964 |
| 17 | 66829954736 |
| 18 | 276135664664 |
| 19 | 1138932645056 |
| 20 | 4690042582664 |
| 21 | 19285299964256 |
| 22 | 79196366286704 |
| 23 | 324835930747136 |
| 24 | 1330905207444344 |