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 | 0 |
| 5 | 3 |
| 6 | 4 |
| 7 | 15 |
| 8 | 39 |
| 9 | 122 |
| 10 | 375 |
| 11 | 1212 |
| 12 | 3980 |
| 13 | 13413 |
| 14 | 45966 |
| 15 | 160295 |
| 16 | 566985 |
| 17 | 2032110 |
| 18 | 7368334 |
| 19 | 27000759 |
| 20 | 99891654 |
| 21 | 372788553 |
| 22 | 1402339329 |
| 23 | 5313959388 |
| 24 | 20272563265 |
| 25 | 77822173758 |
| 26 | 300473023929 |
| 27 | 1166377045666 |
| 28 | 4550358858954 |
| 29 | 17835405078273 |
| 30 | 70213720795466 |
| 31 | 277552814035683 |