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A014915
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a(1)=1, a(n) = n*3^(n-1) + a(n-1).
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15
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1, 7, 34, 142, 547, 2005, 7108, 24604, 83653, 280483, 930022, 3055786, 9964519, 32285041, 104029576, 333612088, 1065406345, 3389929279, 10750918570, 33996147910, 107218620331, 337346390797, 1059110761804, 3318547053652, 10379285465677, 32408789311195
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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) = ((2*n-1)*3^n + 1)/4;
a(n) = 7*a(n-1) - 15*a(n-2) + 9*a(n-3);
a(n) = 1 + 2*3 + 3*3^2 + .. + n*3^(n-1);
a(n) = a(n-1) + A027471(n+1). (End)
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MATHEMATICA
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LinearRecurrence[{7, -15, 9}, {1, 7, 34}, 25] (* L. Edson Jeffery, May 08 2015 *)
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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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STATUS
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approved
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