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 | 2 |
| 3 | 18 |
| 4 | 186 |
| 5 | 2120 |
| 6 | 25724 |
| 7 | 325878 |
| 8 | 4260282 |
| 9 | 57048048 |
| 10 | 778483932 |
| 11 | 10786724388 |
| 12 | 151355847012 |
| 13 | 2146336125648 |
| 14 | 30711521221376 |
| 15 | 442862000693438 |
| 16 | 6429286894263738 |
| 17 | 93891870710425440 |
| 18 | 1378379704593824300 |
| 19 | 20330047491994213884 |
| 20 | 301111732041234778316 |
| 21 | 4476705468260134734384 |
| 22 | 66784808491631598524136 |