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 | 1652 |
| 4 | 119550 |
| 5 | 1497328 |
| 6 | 16733124 |
| 7 | 108084480 |
| 8 | 588808172 |
| 9 | 2544811584 |
| 10 | 9516509988 |
| 11 | 31328336284 |
| 12 | 92876219432 |
| 13 | 252846150384 |
| 14 | 638250041288 |
| 15 | 1511780647680 |
| 16 | 3387237676950 |
| 17 | 7228330859840 |
| 18 | 14769380958438 |
| 19 | 29023337216604 |
| 20 | 55108233751768 |
| 21 | 101433859301088 |