A281565 Number of 3Xn 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.

0, 1, 68, 621, 2426, 6955, 16656, 36578, 76332, 153813, 303761, 591012, 1135722, 2162149, 4084667, 7664486, 14298612, 26540583, 49040949, 90250160, 165483166, 302426113, 551024879, 1001197818, 1814514216, 3280781211, 5918961481

Offset

1,3

Comments

Row 3 of A281563.

Links

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

Formula

Empirical: a(n) = 6*a(n-1) -15*a(n-2) +26*a(n-3) -45*a(n-4) +66*a(n-5) -73*a(n-6) +78*a(n-7) -78*a(n-8) +56*a(n-9) -36*a(n-10) +24*a(n-11) -8*a(n-12) for n>20

Example

Some solutions for n=4
..0..1..1..0. .0..1..1..1. .0..1..1..0. .0..1..0..1. .0..0..1..1
..1..0..1..1. .0..0..0..0. .1..0..0..1. .0..0..1..1. .0..0..1..1
..1..0..0..0. .1..1..1..0. .0..0..1..1. .1..0..0..1. .0..1..0..1

Crossrefs

Cf. A281563.

Sequence in context: A027850 A372401 A248467 * A281883 A282333 A244440

Adjacent sequences: A281562 A281563 A281564 * A281566 A281567 A281568

Keyword

nonn

Author

R. H. Hardin, Jan 24 2017

Status

approved