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 | 4 |
| 3 | 14 |
| 4 | 154 |
| 5 | 924 |
| 6 | 6699 |
| 7 | 44979 |
| 8 | 310764 |
| 9 | 2123554 |
| 10 | 14571974 |
| 11 | 99833524 |
| 12 | 684385079 |
| 13 | 4690541639 |
| 14 | 32150245204 |
| 15 | 220358978774 |
| 16 | 1510368355474 |
| 17 | 10352204457804 |
| 18 | 70955102255139 |
| 19 | 486333408161979 |
| 20 | 3333379024971324 |
| 21 | 22847319059525674 |
| 22 | 156597856242950654 |