A220612 Number of ways to reciprocally link elements of an nX6 array either to themselves or to exactly two horizontal and vertical neighbors, without consecutive collinear links

1, 13, 43, 281, 1277, 7041, 34981, 183920, 937663, 4861869, 24977087, 128971605, 664092737, 3424806465, 17647051243, 90973240309, 468858278192, 2416753993341, 12456282450653, 64204249763017, 330924094972255, 1705685462529549

Offset

1,2

Comments

Column 6 of A220614

Links

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

Formula

Empirical: a(n) = 3*a(n-1) +23*a(n-2) -40*a(n-3) -160*a(n-4) +190*a(n-5) +441*a(n-6) -369*a(n-7) -513*a(n-8) +278*a(n-9) +240*a(n-10) -64*a(n-11) -39*a(n-12) +3*a(n-13) +a(n-14)

Example

Some solutions for n=3 0=self 2=n 4=w 6=e 8=s (reciprocal directions total 10)
.68.48.00.00.00.00...00.00.00.68.48.00...68.48.68.48.00.00...68.48.68.48.68.48
.26.24.00.00.68.48...00.00.00.26.24.00...26.24.26.24.68.48...26.24.26.24.26.24
.00.00.00.00.26.24...00.00.00.00.00.00...00.00.00.00.26.24...00.00.00.00.00.00

Crossrefs

Sequence in context: A242548 A104115 A063650 * A144236 A082689 A228505

Adjacent sequences: A220609 A220610 A220611 * A220613 A220614 A220615

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved