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 | 12 |
| 3 | 55 |
| 4 | 240 |
| 5 | 999 |
| 6 | 4060 |
| 7 | 16335 |
| 8 | 65472 |
| 9 | 262063 |
| 10 | 1048476 |
| 11 | 4194183 |
| 12 | 16777072 |
| 13 | 67108695 |
| 14 | 268435260 |
| 15 | 1073741599 |
| 16 | 4294967040 |
| 17 | 17179868895 |
| 18 | 68719476412 |
| 19 | 274877906583 |
| 20 | 1099511627376 |
| 21 | 4398046510663 |
| 22 | 17592186043932 |