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 A204565 Number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements, and new values 0..3 introduced in row major order. 1
 8, 42, 256, 1682, 11448, 79162, 551216, 3849762, 26922088, 188375882, 1318394976, 9228056242, 64594267928, 452153498202, 3165055355536, 22155330093122, 155087138464968, 1085609452694122, 7599264619176896, 53194847685192402 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A204572. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 11*a(n-1) - 31*a(n-2) + 21*a(n-3). Conjectures from Colin Barker, Jun 07 2018: (Start) G.f.: 2*x*(4 - 23*x + 21*x^2) / ((1 - x)*(1 - 3*x)*(1 - 7*x)). a(n) = 1/3 + 3^n + (2*7^n)/3. (End) EXAMPLE Some solutions for n=4: ..0..0....0..0....0..0....0..0....0..0....0..1....0..1....0..0....0..1....0..0 ..1..0....0..0....0..0....0..0....0..0....0..0....1..0....0..0....1..0....0..0 ..0..1....0..0....0..0....0..0....0..1....0..0....0..0....0..0....0..0....1..0 ..1..0....0..1....0..1....1..0....1..1....1..0....0..1....0..0....2..0....2..1 ..0..0....1..2....1..0....1..1....0..1....2..1....0..0....0..0....0..2....2..2 CROSSREFS Cf. A204572. Sequence in context: A346980 A047759 A047772 * A020068 A266474 A238723 Adjacent sequences: A204562 A204563 A204564 * A204566 A204567 A204568 KEYWORD nonn AUTHOR R. H. Hardin, Jan 16 2012 STATUS approved

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Last modified December 2 08:36 EST 2022. Contains 358493 sequences. (Running on oeis4.)