A162088 Number of n X n 0..5 arrays with rows and columns, considered as 6-ary numbers, in nondecreasing order.
6, 421, 520017, 13111482259, 7470491620551006, 103937249022030445057526
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.