cp's OEIS Frontend

A220621 T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor.

%I A220621 #6 Jul 23 2025 01:18:27
%S A220621 1,2,1,3,7,1,5,21,22,1,8,87,125,71,1,13,317,1189,765,228,1,21,1215,
%T A220621 9176,17084,4657,733,1,34,4565,76955,282777,243119,28373,2356,1,55,
%U A220621 17287,624227,5280827,8608738,3466455,172833,7573,1,89,65261,5131406,93905509
%N A220621 T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor.
%C A220621 Table starts
%C A220621 .1......2..........3..............5..................8.....................13
%C A220621 .1......7.........21.............87................317...................1215
%C A220621 .1.....22........125...........1189...............9176..................76955
%C A220621 .1.....71........765..........17084.............282777................5280827
%C A220621 .1....228.......4657.........243119............8608738..............356768525
%C A220621 .1....733......28373........3466455..........262680517............24177895648
%C A220621 .1...2356.....172833.......49406943.........8011414792..........1637496710797
%C A220621 .1...7573....1052829......704243629.......244357686173........110916199227139
%C A220621 .1..24342....6413369....10038098456......7453056468816.......7512747980759983
%C A220621 .1..78243...39067429...143080761421....227323314349577.....508867505795261823
%C A220621 .1.251498..237981569..2039439299333...6933510501158596...34467532553765146717
%C A220621 .1.808395.1449678893.29069688249415.211476640729594693.2334617570886588879553
%H A220621 R. H. Hardin, <a href="/A220621/b220621.txt">Table of n, a(n) for n = 1..199</a>
%e A220621 Some solutions for n=3 k=4 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
%e A220621 ..6..4..6..4....9..9..6..4....6..4..9..7....6..4..6..4....6..4..6..4
%e A220621 ..0..7..6..4....0..1..1..0....0..0..3..1....0..0..7..0....0..6..4..0
%e A220621 ..3..6..4..0....6..4..0..0....0..6..4..0....0..3..6..4....6..4..6..4
%Y A220621 Column 2 is A030186
%Y A220621 Row 1 is A000045(n+1)
%Y A220621 Row 2 is A177369
%K A220621 nonn,tabl
%O A220621 1,2
%A A220621 _R. H. Hardin_ Dec 17 2012