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 | 4 |
| 1 | 19 |
| 2 | 109 |
| 3 | 649 |
| 4 | 3889 |
| 5 | 23329 |
| 6 | 139969 |
| 7 | 839809 |
| 8 | 5038849 |
| 9 | 30233089 |
| 10 | 181398529 |
| 11 | 1088391169 |
| 12 | 6530347009 |
| 13 | 39182082049 |
| 14 | 235092492289 |
| 15 | 1410554953729 |
| 16 | 8463329722369 |
| 17 | 50779978334209 |
| 18 | 304679870005249 |
| 19 | 1828079220031489 |
| 20 | 10968475320188929 |