login
A198248
Number of 2nX6 0..4 arrays with values 0..4 introduced in row major order and each element equal to exactly two horizontal and vertical neighbors
1
2, 40, 1675, 81440, 4059950, 203087097, 10164141586, 508740409496, 25464106707391, 1274565023173456, 63796351813851410, 3193226785065121249, 159831987739494226958, 8000141016276333546184, 400434589880788614683443
OFFSET
1,1
COMMENTS
Column 3 of A198253
LINKS
FORMULA
Empirical: a(n) = 72*a(n-1) -1224*a(n-2) +6597*a(n-3) -19006*a(n-4) +172500*a(n-5) -532320*a(n-6) -1349230*a(n-7) -4127885*a(n-8) +33277832*a(n-9) +64772160*a(n-10) -69056031*a(n-11) -640524524*a(n-12) -747043292*a(n-13) +1639831968*a(n-14) +4384055040*a(n-15) +3468395008*a(n-16) -6524486656*a(n-17) -12366217216*a(n-18) -2784755712*a(n-19) +4957667328*a(n-20) +8589934592*a(n-21)
EXAMPLE
Some solutions for n=4
..0..0..1..1..2..2....0..0..1..1..2..2....0..0..1..1..2..2....0..0..1..1..1..1
..0..0..1..1..2..2....0..0..1..1..2..2....0..0..1..1..2..2....0..0..1..2..2..1
..2..2..3..3..0..0....3..3..2..2..4..4....1..1..3..3..4..4....1..1..1..2..2..1
..2..2..3..3..0..0....3..3..2..2..4..4....1..1..3..3..4..4....1..0..0..1..1..1
..4..4..4..4..4..4....2..2..1..1..0..0....4..4..4..4..2..2....1..0..0..1..0..0
..4..1..1..3..3..4....2..2..1..1..0..0....4..0..0..4..2..2....1..1..1..1..0..0
..4..1..1..3..3..4....4..4..2..2..1..1....4..0..0..4..0..0....3..3..0..0..3..3
..4..4..4..4..4..4....4..4..2..2..1..1....4..4..4..4..0..0....3..3..0..0..3..3
CROSSREFS
Sequence in context: A286124 A275931 A099707 * A261732 A292418 A163826
KEYWORD
nonn
AUTHOR
R. H. Hardin Oct 22 2011
STATUS
approved