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 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 14 |
| 5 | 44 |
| 6 | 150 |
| 7 | 520 |
| 8 | 1850 |
| 9 | 6696 |
| 10 | 24602 |
| 11 | 91500 |
| 12 | 343846 |
| 13 | 1303572 |
| 14 | 4979822 |
| 15 | 19150352 |
| 16 | 74075890 |
| 17 | 288022160 |
| 18 | 1125076210 |
| 19 | 4413061972 |
| 20 | 17375007294 |
| 21 | 68641377980 |
| 22 | 272014578822 |
| 23 | 1081009104664 |
| 24 | 4307221752874 |
| 25 | 17203123381304 |