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 | -3 |
| 2 | 1 |
| 3 | 25 |
| 4 | 121 |
| 5 | 2041 |
| 6 | 8185 |
| 7 | 131065 |
| 8 | 524281 |
| 9 | 8388601 |
| 10 | 536870905 |
| 11 | 2147483641 |
| 12 | 137438953465 |
| 13 | 2199023255545 |
| 14 | 8796093022201 |
| 15 | 140737488355321 |
| 16 | 9007199254740985 |
| 17 | 576460752303423481 |
| 18 | 2305843009213693945 |
| 19 | 147573952589676412921 |
| 20 | 2361183241434822606841 |