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 | -5 |
| 2 | -25 |
| 3 | -125 |
| 4 | 0 |
| 5 | 13125 |
| 6 | 243750 |
| 7 | 2921875 |
| 8 | 22343750 |
| 9 | 0 |
| 10 | -3658984375 |
| 11 | -77669921875 |
| 12 | -1031953125000 |
| 13 | -8564355468750 |
| 14 | 0 |
| 15 | 1584797607421875 |
| 16 | 35256063232421875 |
| 17 | 487629016113281250 |
| 18 | 4190289337158203125 |
| 19 | 0 |
| 20 | -821167214355468750000 |
| 21 | -18710068030548095703125 |
| 22 | -264378336959838867187500 |