A220635 Number of ways to reciprocally link elements of an 5Xn array either to themselves or to exactly two horizontal or antidiagonal neighbors.

1, 1, 8, 114, 1481, 17527, 201903, 2329448, 26904225, 310837917, 3591561452, 41499180881, 479508472309, 5540546671074, 64018957168901, 739714921940047, 8547125318062702, 98758781455779205, 1141120102778497151

Offset: 1

Author

R. H. Hardin Dec 17 2012

Keywords

• nonn

Comments

Row 5 of A220632

Examples

			Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
.00.67.47...00.67.47...00.00.00...00.00.00...00.00.00...00.67.47...00.00.00
.36.34.00...36.34.00...00.00.00...00.67.47...00.67.47...36.34.00...00.00.00
.00.67.47...00.00.00...00.00.00...36.34.00...36.34.00...00.00.00...00.00.00
.36.34.00...00.67.47...00.67.47...00.67.47...00.00.00...00.00.00...00.00.00
.00.00.00...36.34.00...36.34.00...36.34.00...00.00.00...00.00.00...00.00.00
		

Links

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

Formula

Empirical: a(n) = 16*a(n-1) -39*a(n-2) -186*a(n-3) +419*a(n-4) +1024*a(n-5) -1049*a(n-6) -2258*a(n-7) +861*a(n-8) +2000*a(n-9) -133*a(n-10) -586*a(n-11) -16*a(n-12) +32*a(n-13) for n>17