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 | 2 |
| 2 | 3 |
| 3 | 9 |
| 4 | 30 |
| 5 | 110 |
| 6 | 423 |
| 7 | 1706 |
| 8 | 7085 |
| 9 | 30186 |
| 10 | 131071 |
| 11 | 578194 |
| 12 | 2583377 |
| 13 | 11667874 |
| 14 | 53180604 |
| 15 | 244301512 |
| 16 | 1129947243 |
| 17 | 5257592237 |
| 18 | 24592945975 |
| 19 | 115578827200 |
| 20 | 545478791124 |
| 21 | 2584216074295 |
| 22 | 12285025045259 |
| 23 | 58584860422121 |
| 24 | 280181867792399 |
| 25 | 1343499543045511 |
| 26 | 6457845289959966 |