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 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 4 |
| 5 | 13 |
| 6 | 40 |
| 7 | 130 |
| 8 | 432 |
| 9 | 1466 |
| 10 | 5056 |
| 11 | 17672 |
| 12 | 62460 |
| 13 | 222853 |
| 14 | 801592 |
| 15 | 2903626 |
| 16 | 10582816 |
| 17 | 38781310 |
| 18 | 142805056 |
| 19 | 528134764 |
| 20 | 1960825672 |
| 21 | 7305767602 |
| 22 | 27307800400 |
| 23 | 102371942932 |
| 24 | 384806950624 |
| 25 | 1450038737668 |
| 26 | 5476570993440 |
| 27 | 20727983587220 |
| 28 | 78606637060012 |