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A080675
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a(n) = (5*4^n - 8)/6.
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7
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2, 12, 52, 212, 852, 3412, 13652, 54612, 218452, 873812, 3495252, 13981012, 55924052, 223696212, 894784852, 3579139412, 14316557652, 57266230612, 229064922452, 916259689812, 3665038759252, 14660155037012, 58640620148052, 234562480592212, 938249922368852
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OFFSET
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1,1
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COMMENTS
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These numbers have a simple binary pattern: 10,1100,110100,11010100,1101010100, ... i.e., the n-th term has a binary expansion 1(10){n-1}0, that is, there are n-1 10's between the most significant 1 and the least significant 0.
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LINKS
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FORMULA
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a(1)=2, a(2)=12, a(n)=5*a(n-1)-4*a(n-2). - Harvey P. Dale, Oct 16 2012
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MATHEMATICA
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(5*4^Range[30]-8)/6 (* or *) LinearRecurrence[{5, -4}, {2, 12}, 30] (* Harvey P. Dale, Oct 16 2012 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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