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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 66 |
| 5 | 450 |
| 6 | 3679 |
| 7 | 35260 |
| 8 | 388511 |
| 9 | 4844584 |
| 10 | 67502450 |
| 11 | 1039929756 |
| 12 | 17556193609 |
| 13 | 322321551868 |
| 14 | 6393505020803 |
| 15 | 136245752898586 |
| 16 | 3103879644045050 |
| 17 | 75268872986970840 |
| 18 | 1935571325829192247 |
| 19 | 52605265683008056660 |
| 20 | 1506530437404419817467 |