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 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 16 |
| 6 | 60 |
| 7 | 212 |
| 8 | 728 |
| 9 | 2444 |
| 10 | 8064 |
| 11 | 26256 |
| 12 | 84576 |
| 13 | 270048 |
| 14 | 855936 |
| 15 | 2696080 |
| 16 | 8446912 |
| 17 | 26341696 |
| 18 | 81812544 |
| 19 | 253181888 |
| 20 | 781005440 |
| 21 | 2402311616 |
| 22 | 7370247168 |
| 23 | 22558917120 |
| 24 | 68901651456 |
| 25 | 210037106688 |
| 26 | 639127277568 |
| 27 | 1941624275200 |
| 28 | 5889576530944 |
| 29 | 17839902853120 |