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 | 4 |
| 5 | 19 |
| 6 | 70 |
| 7 | 261 |
| 8 | 914 |
| 9 | 3177 |
| 10 | 10816 |
| 11 | 36566 |
| 12 | 122552 |
| 13 | 408840 |
| 14 | 1358032 |
| 15 | 4497995 |
| 16 | 14862112 |
| 17 | 49019688 |
| 18 | 161449208 |
| 19 | 531152855 |
| 20 | 1745892452 |
| 21 | 5734722698 |
| 22 | 18826352472 |
| 23 | 61777432510 |
| 24 | 202648614072 |
| 25 | 664569581090 |
| 26 | 2178948104572 |
| 27 | 7143067052707 |
| 28 | 23413795288008 |