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

5,2

Links

Table of n, a(n) for n=5..26.

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)

Crossrefs

Sequence in context: A253824 A218414 A328133 * A159207 A101705 A034620

Adjacent sequences: A146120 A146121 A146122 * A146124 A146125 A146126

Keyword

nonn

Author

R. H. Hardin, Apr 14 2009

Status

approved