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 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 9 |
| 7 | 20 |
| 8 | 47 |
| 9 | 112 |
| 10 | 274 |
| 11 | 678 |
| 12 | 1709 |
| 13 | 4346 |
| 14 | 11176 |
| 15 | 28966 |
| 16 | 75656 |
| 17 | 198814 |
| 18 | 525496 |
| 19 | 1395758 |
| 20 | 3723986 |
| 21 | 9975314 |
| 22 | 26817655 |
| 23 | 72332320 |
| 24 | 195679137 |
| 25 | 530814386 |
| 26 | 1443556739 |
| 27 | 3934880554 |
| 28 | 10748839215 |
| 29 | 29420919456 |
| 30 | 80678144437 |
| 31 | 221618678694 |