A222939 Number of n X 1 0..4 arrays with no element equal to another at a city block distance of exactly two, and new values 0..4 introduced in row major order.

1, 2, 3, 7, 20, 66, 238, 902, 3510, 13846, 54998, 219222, 875350, 3498326, 13987158, 55936342, 223720790, 894834006, 3579237718, 14316754262, 57266623830, 229065708886, 916261262678, 3665041904982, 14660161328470, 58640632730966

Offset

1,2

Comments

Column 1 of A222944.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n>5.

Conjectures from Colin Barker, Aug 16 2018: (Start)

G.f.: x*(1 + x)*(1 - 6*x + 9*x^2 - 3*x^3) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).

a(n) = (256 + 9*2^(3+n) + 5*4^n) / 384 for n>2.

(End)

Example

All solutions for n=3:
..0....0....0
..0....1....1
..1....2....1

Crossrefs

Cf. A222944.

Sequence in context: A052402 A372076 A300041 * A222867 A222776 A222890

Adjacent sequences: A222936 A222937 A222938 * A222940 A222941 A222942

Keyword

nonn

Author

R. H. Hardin, Mar 09 2013

Status

approved