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 | -2 |
| 3 | -7 |
| 4 | -35 |
| 5 | -226 |
| 6 | -1769 |
| 7 | -16003 |
| 8 | -159998 |
| 9 | -1669645 |
| 10 | -16203509 |
| 11 | -85724926 |
| 12 | 2606965153 |
| 13 | 154547040023 |
| 14 | 6047755681150 |
| 15 | 217270016433329 |
| 16 | 7721994442008061 |
| 17 | 279057037146008702 |
| 18 | 10378357435103977207 |
| 19 | 399487271346562859045 |
| 20 | 15957215240554330744066 |