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 | -3 |
| 3 | 13 |
| 4 | -71 |
| 5 | 441 |
| 6 | -2699 |
| 7 | 9157 |
| 8 | 206193 |
| 9 | -8443151 |
| 10 | 236126701 |
| 11 | -6169406979 |
| 12 | 161388751657 |
| 13 | -4327824442967 |
| 14 | 120012465557349 |
| 15 | -3450029411174219 |
| 16 | 102741264191105761 |
| 17 | -3160671409312412703 |
| 18 | 99982488984008583133 |
| 19 | -3230094912866216253971 |
| 20 | 105481073534842477321881 |
| 21 | -3423260541695907002392679 |