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 | 561 |
| 4 | 4433 |
| 5 | 35031 |
| 6 | 276827 |
| 7 | 2187585 |
| 8 | 17287073 |
| 9 | 136608591 |
| 10 | 1079529611 |
| 11 | 8530826457 |
| 12 | 67413620993 |
| 13 | 532726379847 |
| 14 | 4209793089371 |
| 15 | 33267280400913 |
| 16 | 262889866978817 |
| 17 | 2077449112980255 |
| 18 | 16416740845208075 |
| 19 | 129730917736941417 |
| 20 | 1025179795159015841 |