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 | -7 |
| 3 | -33 |
| 4 | 105 |
| 5 | 5199 |
| 6 | 64953 |
| 7 | -46593 |
| 8 | -21769335 |
| 9 | -497664081 |
| 10 | -1941272487 |
| 11 | 256114020447 |
| 12 | 9566995408425 |
| 13 | 99966666676239 |
| 14 | -6245895772363527 |
| 15 | -366865939437422913 |
| 16 | -6924777575908002615 |
| 17 | 259022993102904450159 |
| 18 | 24387711970312991335833 |
| 19 | 716398360186298080983327 |