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) |
|---|---|
| 1 | 4 |
| 2 | 15 |
| 3 | 209 |
| 4 | 1116 |
| 5 | 3807 |
| 6 | 53985 |
| 7 | 287844 |
| 8 | 982255 |
| 9 | 13927857 |
| 10 | 74262716 |
| 11 | 253417919 |
| 12 | 3593333185 |
| 13 | 19159492804 |
| 14 | 65380840911 |
| 15 | 927066033809 |
| 16 | 4943074880796 |
| 17 | 16868003537055 |
| 18 | 239179443389601 |
| 19 | 1275294159752484 |
| 20 | 4351879531719343 |
| 21 | 61707369328483185 |