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 | 2 |
| 4 | 32 |
| 5 | 338 |
| 6 | 3560 |
| 7 | 40058 |
| 8 | 492664 |
| 9 | 6647666 |
| 10 | 98210192 |
| 11 | 1581844994 |
| 12 | 27642067000 |
| 13 | 521491848218 |
| 14 | 10572345303576 |
| 15 | 229332715217954 |
| 16 | 5301688511602448 |
| 17 | 130152723055769810 |
| 18 | 3381930236770946120 |
| 19 | 92738693031618794378 |
| 20 | 2676532576838728227352 |