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 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 2 |
| 7 | 6 |
| 8 | 22 |
| 9 | 86 |
| 10 | 342 |
| 11 | 1366 |
| 12 | 5335 |
| 13 | 20960 |
| 14 | 82464 |
| 15 | 324528 |
| 16 | 1277104 |
| 17 | 5025200 |
| 18 | 19770800 |
| 19 | 77789489 |
| 20 | 306071370 |
| 21 | 1204272270 |
| 22 | 4738336974 |
| 23 | 18643463374 |
| 24 | 73354544590 |
| 25 | 288620849614 |
| 26 | 1135607911375 |
| 27 | 4468164041216 |
| 28 | 17580442344960 |