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 | 1 |
| 2 | 1 |
| 3 | -5 |
| 4 | -23 |
| 5 | 1 |
| 6 | 601 |
| 7 | 7771 |
| 8 | 26545 |
| 9 | -401183 |
| 10 | -6965999 |
| 11 | -42828389 |
| 12 | 528611161 |
| 13 | 15543020065 |
| 14 | 141983039017 |
| 15 | -2393449681349 |
| 16 | -83586615493919 |
| 17 | -708151768946879 |
| 18 | 15447932991283105 |
| 19 | 635290179334026427 |
| 20 | 7146984268771158601 |
| 21 | -162583738763505944639 |