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 A201271 Number of n X 2 0..2 arrays with every row and column nondecreasing rightwards and downwards, and the number of instances of each value within one of each other. 2
 1, 3, 5, 4, 12, 16, 9, 27, 33, 16, 48, 56, 25, 75, 85, 36, 108, 120, 49, 147, 161, 64, 192, 208, 81, 243, 261, 100, 300, 320, 121, 363, 385, 144, 432, 456, 169, 507, 533, 196, 588, 616, 225, 675, 705, 256, 768, 800, 289, 867, 901, 324, 972, 1008, 361, 1083, 1121, 400, 1200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..10000 (terms n = 1..210 from R. H. Hardin) FORMULA a(n) = 3*a(n-3) -3*a(n-6) +a(n-9). Subsequences for n modulo 3 = 1,2,0: p=(n+2)/3: a(n) = 3*p^2 q=(n+1)/3: a(n) = 3*q^2 + 2*q r=(n+0)/3: a(n) = r^2 + 2*r + 1. G.f.: 1+x*(3 + 5*x + 4*x^2 + 3*x^3 + x^4 - 3*x^5 + x^8) / ((1 - x)^3*(1 + x + x^2)^3). - Colin Barker, May 22 2018 EXAMPLE Some solutions for n=5: ..0..1....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..1....0..0 ..0..1....0..1....0..0....0..1....0..1....0..1....0..0....0..2....0..1....0..2 ..0..1....0..1....1..2....1..1....1..1....1..2....1..1....0..2....0..2....1..2 ..0..2....1..2....1..2....2..2....1..2....1..2....1..2....1..2....1..2....1..2 ..2..2....2..2....1..2....2..2....2..2....2..2....2..2....1..2....2..2....1..2 CROSSREFS Column 2 of A201277. Sequence in context: A127397 A284048 A326119 * A324779 A167808 A161353 Adjacent sequences: A201268 A201269 A201270 * A201272 A201273 A201274 KEYWORD nonn,easy AUTHOR R. H. Hardin, Nov 29 2011 EXTENSIONS a(0)=1 prepended by Alois P. Heinz, Mar 18 2024 STATUS approved

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Last modified September 13 20:16 EDT 2024. Contains 375910 sequences. (Running on oeis4.)