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 | 18 |
| 3 | 135 |
| 4 | 1215 |
| 5 | 12636 |
| 6 | 147987 |
| 7 | 1917999 |
| 8 | 27162540 |
| 9 | 416236401 |
| 10 | 6848207775 |
| 11 | 120206639790 |
| 12 | 2239278203277 |
| 13 | 44074161731151 |
| 14 | 913065539247018 |
| 15 | 19843943547060315 |
| 16 | 451135755042249987 |
| 17 | 10701182793462338052 |
| 18 | 264250529777677991751 |
| 19 | 6779171511882363638619 |
| 20 | 180350988089950776032172 |