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 | 4 |
| 4 | -3 |
| 5 | -44 |
| 6 | 595 |
| 7 | -5214 |
| 8 | 36953 |
| 9 | -176840 |
| 10 | -498969 |
| 11 | 31239550 |
| 12 | -605916971 |
| 13 | 9001842708 |
| 14 | -110410388101 |
| 15 | 998140500826 |
| 16 | -1114748107215 |
| 17 | -247879285927184 |
| 18 | 8410011463871695 |
| 19 | -201620611378992906 |
| 20 | 4024515940445770541 |
| 21 | -66832538504513547380 |