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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 15 |
| 5 | 52 |
| 6 | 190 |
| 7 | 696 |
| 8 | 2674 |
| 9 | 10480 |
| 10 | 42732 |
| 11 | 178480 |
| 12 | 770836 |
| 13 | 3411024 |
| 14 | 15538120 |
| 15 | 72446752 |
| 16 | 346550520 |
| 17 | 1694394496 |
| 18 | 8477167504 |
| 19 | 43287312960 |
| 20 | 225707308912 |
| 21 | 1199526928960 |
| 22 | 6498288708576 |
| 23 | 35836282708864 |
| 24 | 201160191642400 |
| 25 | 1148165325126912 |
| 26 | 6662315102507200 |
| 27 | 39268797697682176 |