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 | 9 |
| 2 | 49 |
| 3 | 249 |
| 4 | 1249 |
| 5 | 6249 |
| 6 | 31249 |
| 7 | 156249 |
| 8 | 781249 |
| 9 | 3906249 |
| 10 | 19531249 |
| 11 | 97656249 |
| 12 | 488281249 |
| 13 | 2441406249 |
| 14 | 12207031249 |
| 15 | 61035156249 |
| 16 | 305175781249 |
| 17 | 1525878906249 |
| 18 | 7629394531249 |
| 19 | 38146972656249 |
| 20 | 190734863281249 |