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 | 3 |
| 2 | 21 |
| 3 | 153 |
| 4 | 1041 |
| 5 | 6753 |
| 6 | 42561 |
| 7 | 263553 |
| 8 | 1614081 |
| 9 | 9815553 |
| 10 | 59417601 |
| 11 | 358602753 |
| 12 | 2160005121 |
| 13 | 12993585153 |
| 14 | 78095728641 |
| 15 | 469111242753 |
| 16 | 2816814940161 |
| 17 | 16909479575553 |
| 18 | 101491237191681 |
| 19 | 609084862103553 |
| 20 | 3655058928435201 |