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 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 88 |
| 6 | 370 |
| 7 | 1612 |
| 8 | 7232 |
| 9 | 33304 |
| 10 | 157102 |
| 11 | 757804 |
| 12 | 3731352 |
| 13 | 18720504 |
| 14 | 95519428 |
| 15 | 494733144 |
| 16 | 2596388976 |
| 17 | 13783481424 |
| 18 | 73906300822 |
| 19 | 399722732236 |
| 20 | 2178164438936 |
| 21 | 11946745980632 |
| 22 | 65898275096796 |
| 23 | 365308080119688 |
| 24 | 2033992114316240 |
| 25 | 11369167905107888 |
| 26 | 63769939599193228 |
| 27 | 358804271821028088 |
| 28 | 2024523256299630832 |