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A176805
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a(n) = 3^n + 3*n + 1.
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6
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2, 7, 16, 37, 94, 259, 748, 2209, 6586, 19711, 59080, 177181, 531478, 1594363, 4783012, 14348953, 43046770, 129140215, 387420544, 1162261525, 3486784462, 10460353267, 31381059676, 94143178897, 282429536554, 847288609519
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n)= 5*a(n-1) - 7*a(n-2) + 3*a(n-3).
G.f.: (1+x)*(5*x-2) / ( (3*x-1)*(x-1)^2 ). (End)
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EXAMPLE
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a(7) = (3^7) + (3*7) + 1 = 2209 = 47^2.
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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Corrected (1 replaced by 2, 2209 inserted) by R. J. Mathar, Apr 27 2010
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STATUS
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approved
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