A209370 Number of nX4 1..3 arrays with no element with value z exactly a city block distance of z from another element with value z

35, 129, 242, 968, 3698, 14112, 54450, 208658, 798848, 3065288, 11761250, 45106002, 172980000, 663426738, 2544555122, 9759442050, 37430668832, 143559037778, 550601290962, 2111759107200, 8099354578322, 31063907847200, 119141222480000

Offset

1,1

Comments

Column 4 of A209374

Links

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

Formula

Empirical: a(n) = a(n-1) +4*a(n-2) +13*a(n-3) +38*a(n-4) +56*a(n-5) +20*a(n-6) -107*a(n-7) -179*a(n-8) -5*a(n-9) +123*a(n-10) -11*a(n-11) -105*a(n-12) -74*a(n-13) -16*a(n-14) +25*a(n-15) +19*a(n-16) +6*a(n-17) +3*a(n-18) +2*a(n-20) -a(n-21) for n>23

Example

Some solutions for n=5
..2..1..3..1....2..2..1..3....1..2..1..3....1..3..1..2....2..2..3..1
..1..3..1..3....3..1..3..2....3..1..3..1....2..2..3..1....1..3..1..2
..3..1..2..1....1..3..1..2....2..3..1..3....1..3..1..3....3..1..3..1
..2..3..1..3....3..2..3..1....2..1..3..2....3..1..2..1....1..2..1..3
..2..1..3..2....1..2..1..3....1..3..1..3....1..3..1..3....3..1..3..2

Crossrefs

Sequence in context: A247679 A344013 A225930 * A219717 A220481 A144492

Adjacent sequences: A209367 A209368 A209369 * A209371 A209372 A209373

Keyword

nonn

Author

R. H. Hardin Mar 07 2012

Status

approved