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A145544
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a(n) = 4*(4^n-3^n).
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0
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0, 4, 28, 148, 700, 3124, 13468, 56788, 235900, 969844, 3958108, 16068628, 64983100, 262058164, 1054609948, 4237571668, 17007682300, 68202916084, 273328224988, 1094862581908, 4384099373500, 17550344631604, 70243219939228, 281098403995348, 1124770188696700
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OFFSET
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0,2
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COMMENTS
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Suggested by a discussion on the Sequence Fans Mailing List; the formula is due to Jaume Oliver Lafont.
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LINKS
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FORMULA
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a(n) = 4*A005061(n) = 7*a(n-1)-12*a(n-2). G.f.: 4*x/((4*x-1)*(3*x-1)). [R. J. Mathar, Mar 18 2009]
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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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STATUS
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approved
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