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 A194888 Number of lower triangles of an n X n 0..3 array with new values introduced in row major order 0..3 and no two horizontal or vertical neighbors of any element equal. 1
 1, 3, 24, 192, 1152, 5760, 26880, 118272, 506880, 2119680, 8761344, 35807232, 145539072, 588349440, 2372075520, 9538240512, 38303170560, 153613762560, 615659864064, 2465854390272, 9873068654592, 39518019256320, 158149336104960 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 3 of A194893. LINKS R. H. Hardin, Table of n, a(n) for n = 1..24 FORMULA Empirical (for n>=3): 9*2^(2*n-2) - (1-(-1)^n)*21/8*2^(3*n/2+1/2) - (1+(-1)^n)*15/4*2^(3*n/2) + 6*2^n. - Vaclav Kotesovec, Nov 27 2012 Empirical g.f.: x*(1 - 3*x + 6*x^2 + 96*x^3 + 80*x^4 - 192*x^5) / ((1 - 2*x)*(1 - 4*x)*(1 - 8*x^2)). - Colin Barker, May 05 2018 EXAMPLE Some solutions for 4 X 4:   0        0        0        0        0        0        0        0   0 1      1 2      1 1      1 2      1 2      1 2      1 2      0 1   2 2 3    3 3 0    2 2 3    1 3 3    1 2 3    1 0 0    3 3 0    2 1 0   1 0 3 1  0 1 2 2  3 0 1 2  2 0 1 1  3 0 0 2  2 3 1 2  2 1 0 3  2 3 0 1 CROSSREFS Cf. A194893. Sequence in context: A027324 A122741 A136325 * A103333 A037762 A037650 Adjacent sequences:  A194885 A194886 A194887 * A194889 A194890 A194891 KEYWORD nonn AUTHOR R. H. Hardin, Sep 04 2011 STATUS approved

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Last modified May 20 08:18 EDT 2022. Contains 353852 sequences. (Running on oeis4.)