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 | 0 |
| 4 | 3 |
| 5 | 6 |
| 6 | 21 |
| 7 | 66 |
| 8 | 220 |
| 9 | 744 |
| 10 | 2562 |
| 11 | 8942 |
| 12 | 31569 |
| 13 | 112530 |
| 14 | 404445 |
| 15 | 1464042 |
| 16 | 5332872 |
| 17 | 19532688 |
| 18 | 71893470 |
| 19 | 265778040 |
| 20 | 986416614 |
| 21 | 3674092044 |
| 22 | 13729259586 |
| 23 | 51455182260 |
| 24 | 193369903608 |
| 25 | 728504292576 |
| 26 | 2750904025276 |
| 27 | 10409856537786 |
| 28 | 39470613237645 |
| 29 | 149935171349546 |