A146506 Number of n X n arrays of squares of integers summing to 18 with every element equal to at least one neighbor.
4, 90, 12424, 2808172, 449235282, 107282960684, 5345302912844, 102834566977650
Offset: 2
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.