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 | 0 |
| 1 | 3 |
| 2 | 18 |
| 3 | 81 |
| 4 | 336 |
| 5 | 1359 |
| 6 | 5454 |
| 7 | 21837 |
| 8 | 87372 |
| 9 | 349515 |
| 10 | 1398090 |
| 11 | 5592393 |
| 12 | 22369608 |
| 13 | 89478471 |
| 14 | 357913926 |
| 15 | 1431655749 |
| 16 | 5726623044 |
| 17 | 22906492227 |
| 18 | 91625968962 |
| 19 | 366503875905 |
| 20 | 1466015503680 |
| 21 | 5864062014783 |
| 22 | 23456248059198 |
| 23 | 93824992236861 |