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 | 0 |
| 2 | 4 |
| 3 | -23 |
| 4 | 233 |
| 5 | -2892 |
| 6 | 43764 |
| 7 | -779779 |
| 8 | 15997437 |
| 9 | -371423052 |
| 10 | 9628576948 |
| 11 | -275683093663 |
| 12 | 8640417354593 |
| 13 | -294234689237660 |
| 14 | 10817772136320356 |
| 15 | -427076118244539019 |
| 16 | 18019667955465012597 |
| 17 | -809220593930871751580 |
| 18 | 38537187481365665823844 |