cp's OEIS Frontend

A220688 T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors.

%I A220688 #6 Jul 23 2025 01:22:08
%S A220688 1,1,1,1,4,1,1,12,12,1,1,37,94,37,1,1,114,745,745,114,1,1,351,5851,
%T A220688 15452,5851,351,1,1,1081,46027,312603,312603,46027,1081,1,1,3329,
%U A220688 362057,6349886,15978924,6349886,362057,3329,1,1,10252,2847943,128995678
%N A220688 T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors.
%C A220688 Table starts
%C A220688 .1.....1.........1.............1................1....................1
%C A220688 .1.....4........12............37..............114..................351
%C A220688 .1....12........94...........745.............5851................46027
%C A220688 .1....37.......745.........15452...........312603..............6349886
%C A220688 .1...114......5851........312603.........15978924............822649205
%C A220688 .1...351.....46027.......6349886........822649205.........107713940118
%C A220688 .1..1081....362057.....128995678......42362190063.......14108684022136
%C A220688 .1..3329...2847943....2620320833....2181341369109.....1848014307847883
%C A220688 .1.10252..22401961...53226950200..112319870453715...242044667782801540
%C A220688 .1.31572.176214299.1081210102382.5783510938076077.31702119421997470360
%H A220688 R. H. Hardin, <a href="/A220688/b220688.txt">Table of n, a(n) for n = 1..180</a>
%e A220688 Some solutions for n=3 k=4 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
%e A220688 .00.78.00.00...68.46.47.00...00.78.78.00...68.46.46.47...68.46.47.00
%e A220688 .38.26.46.48...28.37.67.48...38.23.27.78...28.67.34.78...28.38.00.78
%e A220688 .26.46.46.24...23.36.46.24...26.34.36.24...23.00.36.24...26.24.36.24
%Y A220688 Column 2 is A099098
%K A220688 nonn,tabl
%O A220688 1,5
%A A220688 _R. H. Hardin_ Dec 17 2012