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 | 71 |
| 3 | 559 |
| 4 | 4401 |
| 5 | 34649 |
| 6 | 272791 |
| 7 | 2147679 |
| 8 | 16908641 |
| 9 | 133121449 |
| 10 | 1048062951 |
| 11 | 8251382159 |
| 12 | 64962994321 |
| 13 | 511452572409 |
| 14 | 4026657584951 |
| 15 | 31701808107199 |
| 16 | 249587807272641 |
| 17 | 1965000650073929 |
| 18 | 15470417393318791 |
| 19 | 121798338496476399 |