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 | 4 |
| 3 | 21 |
| 4 | 104 |
| 5 | 521 |
| 6 | 2604 |
| 7 | 13021 |
| 8 | 65104 |
| 9 | 325521 |
| 10 | 1627604 |
| 11 | 8138021 |
| 12 | 40690104 |
| 13 | 203450521 |
| 14 | 1017252604 |
| 15 | 5086263021 |
| 16 | 25431315104 |
| 17 | 127156575521 |
| 18 | 635782877604 |
| 19 | 3178914388021 |
| 20 | 15894571940104 |
| 21 | 79472859700521 |
| 22 | 397364298502604 |
| 23 | 1986821492513021 |
| 24 | 9934107462565104 |