A146123 Number of n X n arrays of squares of integers with every (n-3) X (n-3) subblock summing to 4 and every element equal to at least one neighbor.
1, 540, 4120, 12188, 31000, 67216, 129464, 228136, 375388, 585140, 873076, 1256644, 1755056, 2389288, 3182080, 4157936, 5343124, 6765676, 8455388, 10443820, 12764296, 15451904
Offset: 5
Keywords
Formula
Empirical (for n>=8): 147*n^4/2 - 1355*n^3 + 18985*n^2/2 - 29703*n + 34996. - Vaclav Kotesovec, Nov 30 2012
Conjectures from Colin Barker, Mar 23 2018: (Start)
G.f.: x^5*(1 + 535*x + 1430*x^2 - 3022*x^3 + 5865*x^4 - 4405*x^5 + 1564*x^6 - 204*x^7) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>12.
(End)