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 | 29 |
| 3 | 147 |
| 4 | 774 |
| 5 | 4080 |
| 6 | 21489 |
| 7 | 113466 |
| 8 | 598374 |
| 9 | 3155426 |
| 10 | 16642084 |
| 11 | 87770692 |
| 12 | 462903372 |
| 13 | 2441353234 |
| 14 | 12875695490 |
| 15 | 67906455891 |
| 16 | 358138834199 |
| 17 | 1888825058236 |
| 18 | 9961667898631 |
| 19 | 52537860596653 |
| 20 | 277084804179135 |
| 21 | 1461345928848848 |