A099029 Main diagonal of array A099028.
-1, 6, -72, 1608, -58080, 3087648, -226762368, 21986726016, -2720113657344, 418117827310080, -78167762731812864, 17465102642354817024, -4595978556276162551808, 1406897783859319396442112
Offset: 1
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.