A261815 Total number of semimagic squares of order n that can be formed from the numbers 1, ..., n^2.
1, 0, 72, 549504, 4632344409600
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.