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A151657
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Number of permutations of 7 indistinguishable copies of 1..n with exactly 3 adjacent element pairs in decreasing order.
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1
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0, 1225, 818300, 160310458, 22727054364, 2892619063243, 354402440786800, 42837393111682484, 5153280785356119360, 618914057659003904189, 74290570601695876667092, 8915697686087571194412590, 1069916360274028756641650036, 128391238501628502906890984271
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 120^n - (7*n + 1)*36^n + binomial(7*n+1, 2)*8^n - binomial(7*n+1, 3). - Andrew Howroyd, May 07 2020
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PROG
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(PARI) a(n) = {120^n - (7*n + 1)*36^n + binomial(7*n+1, 2)*8^n - binomial(7*n+1, 3)} \\ Andrew Howroyd, May 07 2020
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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