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) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 6 |
| 6 | 7 |
| 7 | 8 |
| 8 | 12 |
| 9 | 16 |
| 10 | 24 |
| 11 | 31 |
| 12 | 48 |
| 13 | 127 |
| 14 | 8191 |
| 15 | 131071 |
| 16 | 524287 |
| 17 | 2147483647 |
| 18 | 2305843009213693951 |
| 19 | 618970019642690137449562111 |
| 20 | 162259276829213363391578010288127 |
| 21 | 170141183460469231731687303715884105727 |