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 | 1 |
| 4 | 61 |
| 5 | -1 |
| 6 | -12491 |
| 7 | -479 |
| 8 | 530629 |
| 9 | 54979 |
| 10 | 1039405 |
| 11 | -4981183 |
| 12 | -9055875786121 |
| 13 | 908993573959 |
| 14 | 288260975797477 |
| 15 | 7874837285353 |
| 16 | -2255621632465386299 |
| 17 | -189404901989770501 |
| 18 | -20038592583515962234111 |
| 19 | 954329155426992424481 |
| 20 | 1731149375200514221429374109 |