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 A222939 Number of n X 1 0..4 arrays with no element equal to another at a city block distance of exactly two, and new values 0..4 introduced in row major order. 1
 1, 2, 3, 7, 20, 66, 238, 902, 3510, 13846, 54998, 219222, 875350, 3498326, 13987158, 55936342, 223720790, 894834006, 3579237718, 14316754262, 57266623830, 229065708886, 916261262678, 3665041904982, 14660161328470, 58640632730966 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 1 of A222944. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n>5. Conjectures from Colin Barker, Aug 16 2018: (Start) G.f.: x*(1 + x)*(1 - 6*x + 9*x^2 - 3*x^3) / ((1 - x)*(1 - 2*x)*(1 - 4*x)). a(n) = (256 + 9*2^(3+n) + 5*4^n) / 384 for n>2. (End) EXAMPLE All solutions for n=3: ..0....0....0 ..0....1....1 ..1....2....1 CROSSREFS Cf. A222944. Sequence in context: A006073 A052402 A300041 * A222867 A222776 A222890 Adjacent sequences: A222936 A222937 A222938 * A222940 A222941 A222942 KEYWORD nonn AUTHOR R. H. Hardin, Mar 09 2013 STATUS approved

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Last modified September 24 22:14 EDT 2023. Contains 365582 sequences. (Running on oeis4.)