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 A235289 T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with every 2X2 subblock having its diagonal sum differing from its antidiagonal sum by 4 (constant stress 1X1 tilings) 9
 20, 40, 40, 68, 68, 68, 136, 104, 104, 136, 236, 188, 148, 188, 236, 472, 304, 248, 248, 304, 472, 836, 572, 380, 380, 380, 572, 836, 1672, 968, 680, 544, 544, 680, 968, 1672, 3020, 1868, 1108, 908, 740, 908, 1108, 1868, 3020, 6040, 3280, 2072, 1400, 1168, 1168 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Table starts ...20...40...68..136..236...472...836..1672..3020..6040.11108.22216.41516 ...40...68..104..188..304...572...968..1868..3280..6428.11624.22988.42544 ...68..104..148..248..380...680..1108..2072..3548..6824.12148.23768.43580 ..136..188..248..380..544...908..1400..2492..4096..7628.13208.25340.45664 ..236..304..380..544..740..1168..1724..2944..4676..8464.14300.26944.47780 ..472..572..680..908.1168..1724..2408..3884..5872.10172.16520.30188.52048 ..836..968.1108.1400.1724..2408..3220..4952..7196.12008.18868.33560.56444 .1672.1868.2072.2492.2944..3884..4952..7196..9952.15788.23672.40412.65344 .3020.3280.3548.4096.4676..5872..7196..9952.13220.20080.28988.47776.74756 .6040.6428.6824.7628.8464.10172.12008.15788.20080.28988.39944.62828.93904 Empirical: T(n,k)=Number of (n+1)X(k+1) 0..2+i arrays with every 2X2 subblock having its diagonal sum differing from its antidiagonal sum by 2+2*i (constant stress 1X1 tilings) for i=1..4(..?) LINKS R. H. Hardin, Table of n, a(n) for n = 1..568 FORMULA Empirical for column k (the recurrence for k=2..7 also works for k=1; apparently every row and column satisfies the same order 6 recurrence): diagonal: a(n) = a(n-1) +9*a(n-2) -9*a(n-3) -26*a(n-4) +26*a(n-5) +24*a(n-6) -24*a(n-7) k=1: a(n) = 2*a(n-1) +3*a(n-2) -6*a(n-3) k=2..7: a(n) = 3*a(n-1) +3*a(n-2) -15*a(n-3) +4*a(n-4) +18*a(n-5) -12*a(n-6) EXAMPLE Some solutions for n=4 k=4 ..2..0..2..0..2....2..0..2..0..1....2..1..2..0..2....1..3..1..3..2 ..1..3..1..3..1....1..3..1..3..0....0..3..0..2..0....2..0..2..0..3 ..3..1..3..1..3....2..0..2..0..1....3..2..3..1..3....0..2..0..2..1 ..0..2..0..2..0....1..3..1..3..0....0..3..0..2..0....2..0..2..0..3 ..2..0..2..0..2....2..0..2..0..1....3..2..3..1..3....0..2..0..2..1 CROSSREFS Sequence in context: A333234 A040380 A154044 * A296764 A046794 A104153 Adjacent sequences:  A235286 A235287 A235288 * A235290 A235291 A235292 KEYWORD nonn,tabl AUTHOR R. H. Hardin, Jan 05 2014 STATUS approved

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Last modified December 2 13:34 EST 2021. Contains 349444 sequences. (Running on oeis4.)