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 | 3 |
| 3 | 1 |
| 4 | 19 |
| 5 | 81 |
| 6 | 539 |
| 7 | 3881 |
| 8 | 32019 |
| 9 | 294961 |
| 10 | 3006859 |
| 11 | 33608121 |
| 12 | 408778499 |
| 13 | 5375855681 |
| 14 | 76017801339 |
| 15 | 1150262909641 |
| 16 | 18546246267379 |
| 17 | 317444672651601 |
| 18 | 5748938114157419 |
| 19 | 109829779507865561 |
| 20 | 2207493511046751459 |
| 21 | 46566125370108071521 |
| 22 | 1028660983526344785499 |