A220565 Number of ways to reciprocally link elements of an 4Xn array either to themselves or to exactly one horizontal or antidiagonal neighbor.
1, 34, 292, 3966, 45966, 561636, 6743873, 81437539, 981628768, 11839220919, 142763980945, 1721628751022, 20761198193082, 250361650578082, 3019134246246588, 36408038586112352, 439048064386701057
Offset: 1
Keywords
Examples
Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10) ..0..6..4....0..6..4....0..6..4....0..7..0....0..0..0....6..4..0....6..4..0 ..0..0..0....0..7..0....0..7..0....3..0..0....6..4..0....0..6..4....0..7..0 ..0..7..0....3..6..4....3..6..4....6..4..7....0..6..4....0..7..7....3..0..0 ..3..0..0....0..6..4....0..0..0....0..3..0....0..6..4....3..3..0....0..0..0
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = 4*a(n-1) +84*a(n-2) +194*a(n-3) -338*a(n-4) -1077*a(n-5) +616*a(n-6) +1932*a(n-7) -788*a(n-8) -1136*a(n-9) +325*a(n-10) +284*a(n-11) -48*a(n-12) -30*a(n-13) +2*a(n-14) +a(n-15)
Comments