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 | 4 |
| 2 | 6 |
| 3 | 36 |
| 4 | 126 |
| 5 | 540 |
| 6 | 2034 |
| 7 | 8316 |
| 8 | 32760 |
| 9 | 131544 |
| 10 | 524250 |
| 11 | 2099196 |
| 12 | 8388450 |
| 13 | 33562620 |
| 14 | 134217594 |
| 15 | 536903100 |
| 16 | 2147483520 |
| 17 | 8590065660 |
| 18 | 34359735816 |
| 19 | 137439477756 |
| 20 | 549755813250 |
| 21 | 2199025344348 |
| 22 | 8796093020154 |