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 | 7 |
| 5 | 35 |
| 6 | 154 |
| 7 | 637 |
| 8 | 2548 |
| 9 | 9996 |
| 10 | 38760 |
| 11 | 149226 |
| 12 | 572033 |
| 13 | 2187185 |
| 14 | 8351070 |
| 15 | 31865925 |
| 16 | 121580760 |
| 17 | 463991880 |
| 18 | 1771605360 |
| 19 | 6768687870 |
| 20 | 25880277150 |
| 21 | 99035193894 |
| 22 | 379300783092 |
| 23 | 1453986335186 |
| 24 | 5578559816632 |
| 25 | 21422369201800 |
| 26 | 82336410323440 |
| 27 | 316729578421620 |