A220685 Number of ways to reciprocally link elements of an nX5 array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors.

1, 114, 5851, 312603, 15978924, 822649205, 42362190063, 2181341369109, 112319870453715, 5783510938076077, 297801401665428743, 15334225523450669062, 789581475759386788696, 40656693721278204870112

Offset: 1

Author

R. H. Hardin Dec 17 2012

Keywords

• nonn

Comments

Column 5 of A220688

Examples

			Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
.00.78.68.48.78...00.67.46.46.48...00.00.00.68.48...00.78.68.47.00
.36.24.28.23.27...38.68.48.68.24...00.78.00.28.28...38.27.23.78.00
.00.00.26.34.00...26.24.26.24.00...36.24.00.26.24...23.00.36.24.00
		

Links

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

Formula

Empirical: a(n) = 35*a(n-1) +673*a(n-2) +8237*a(n-3) +46927*a(n-4) -112480*a(n-5) -3992526*a(n-6) -35333024*a(n-7) -169366609*a(n-8) -361164394*a(n-9) [phone]*a(n-10) [phone]*a(n-11) [phone]*a(n-12) [phone]*a(n-13) [phone]*a(n-14) -11945755468*a(n-15) -10812604841*a(n-16) [phone]*a(n-17) -8986269878*a(n-18) [phone]*a(n-19) -17268218707*a(n-20) [phone]*a(n-21) [phone]*a(n-22) -5196232889*a(n-23) -236330168*a(n-24) [phone]*a(n-25) -4565014033*a(n-26) [phone]*a(n-27) -1086425818*a(n-28) [phone]*a(n-29) -12788683*a(n-30) -5653764*a(n-31) +2046130*a(n-32) -331034*a(n-33) +12027*a(n-34) +3632*a(n-35) +36*a(n-36) for n>37