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A211906
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Number of lower triangular nXn arrays colored with integers 0 upwards introduced in row major order, with no element equal to any horizontal or vertical neighbor, and containing the value n(n+1)/2-3
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0
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0, 2, 30, 418, 3006, 14201, 51157, 152650, 396538, 926011, 1987151, 3980637, 7530745, 13575108, 23479016, 39178351, 63355567, 99653440, 152931628, 229571396, 337834176, 488279947, 694251735
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OFFSET
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1,2
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COMMENTS
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Column 2 of A211910
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LINKS
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Table of n, a(n) for n=1..23.
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FORMULA
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Empirical: a(n) = (1/128)*n^8 + (1/32)*n^7 - (29/192)*n^6 - (5/16)*n^5 + (193/128)*n^4 - (25/96)*n^3 - (275/96)*n^2 + (49/24)*n + 1 for n>1
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EXAMPLE
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Some solutions for n=4
..0........0........0........0........0........0........0........0
..1.2......1.2......1.2......1.2......1.2......1.2......1.2......1.2
..3.4.5....3.4.5....3.4.5....3.4.2....3.4.5....3.4.5....2.3.4....3.4.5
..6.7.0.8..6.0.1.7..6.3.7.8..5.6.7.3..1.5.6.7..6.2.7.5..5.6.0.7..6.2.6.7
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CROSSREFS
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Sequence in context: A083446 A091345 A147682 * A077517 A060042 A217855
Adjacent sequences: A211903 A211904 A211905 * A211907 A211908 A211909
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin Apr 25 2012
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STATUS
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approved
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