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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -2 |
| 5 | -1 |
| 6 | 5 |
| 7 | 9 |
| 8 | -8 |
| 9 | -41 |
| 10 | -61 |
| 11 | 241 |
| 12 | 770 |
| 13 | -271 |
| 14 | -8649 |
| 15 | -27329 |
| 16 | 106768 |
| 17 | 651521 |
| 18 | 740665 |
| 19 | -18425809 |
| 20 | -107300098 |
| 21 | 399122991 |
| 22 | 5615422669 |
| 23 | 24055184809 |
| 24 | -383354254360 |
| 25 | -3943757411849 |
| 26 | 9276714153611 |
| 27 | 498726356978849 |