cp's OEIS Frontend

A220617 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor.

%I A220617 #6 Jul 23 2025 01:18:00
%S A220617 5,87,1189,17084,243119,3466455,49406943,704243629,10038098456,
%T A220617 143080761421,2039439299333,29069688249415,414352491974681,
%U A220617 5906082889319188,84183915242486395,1199937711608731991
%N A220617 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor.
%C A220617 Column 4 of A220621
%H A220617 R. H. Hardin, <a href="/A220617/b220617.txt">Table of n, a(n) for n = 1..210</a>
%F A220617 Empirical: a(n) = 16*a(n-1) -18*a(n-2) -114*a(n-3) +230*a(n-4) -66*a(n-5) -78*a(n-6) +48*a(n-7) -4*a(n-8) -4*a(n-9) +a(n-10)
%e A220617 Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
%e A220617 ..0..9..6..4....0..0..6..4....0..6..4..0....9..7..0..0....9..7..0..0
%e A220617 ..0..7..1..0....0..0..0..0....0..0..0..7....3..1..6..4....3..1..6..4
%e A220617 ..3..0..0..0....0..0..6..4....0..0..3..0....0..0..0..0....0..6..4..0
%K A220617 nonn
%O A220617 1,1
%A A220617 _R. H. Hardin_ Dec 17 2012