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 A243028 Number of length n+3 0..3 arrays with no four elements in a row with pattern abba (possibly a=b) and new values 0..3 introduced in 0..3 order. 1
 13, 42, 147, 536, 1987, 7414, 27736, 103868, 389129, 1458054, 5463618, 20473754, 76721788, 287502448, 1077370309, 4037278442, 15129079265, 56693899710, 212451684345, 796130077586, 2983375282018, 11179741027060, 41894363838109 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 4*a(n-1) - a(n-2) + 2*a(n-3) - 6*a(n-4) - 2*a(n-5) - 3*a(n-6). Empirical g.f.: x*(13 - 10*x - 8*x^2 - 36*x^3 - 16*x^4 - 14*x^5) / ((1 - x - x^3)*(1 - 3*x - 2*x^2 - 3*x^3)). - Colin Barker, Nov 01 2018 EXAMPLE Some solutions for n=3: ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0 ..1....1....0....0....1....1....0....1....0....1....1....1....1....0....1....0 ..2....0....1....1....0....2....0....1....0....2....0....0....0....0....0....1 ..2....2....0....2....0....3....1....1....1....0....1....2....2....1....1....2 ..3....3....0....3....2....2....2....0....0....1....0....0....3....2....1....1 ..0....0....0....3....0....2....3....1....2....2....2....0....2....0....1....1 CROSSREFS Column 3 of A243033. Sequence in context: A139277 A162265 A233298 * A242544 A301539 A240517 Adjacent sequences:  A243025 A243026 A243027 * A243029 A243030 A243031 KEYWORD nonn AUTHOR R. H. Hardin, May 29 2014 STATUS approved

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Last modified April 10 21:11 EDT 2021. Contains 342856 sequences. (Running on oeis4.)