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Search: id:A014915
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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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+0
9
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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
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n) = ((2n - 1)*3^n + 1)/4 = 7a(n - 1) - 15a(n - 2) + 9a(n - 3) = 1 + 2*3 + 3*3^2 + .. + n*3^(n - 1) = a(n - 1) + A027471(n + 1) - Henry Bottomley (se16(AT)btinternet.com), Dec 18 2000
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MAPLE
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a:=n->sum (3^n-3^j, j=0..n): seq(a(n)/2, n=1..31); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 14 2008]
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CROSSREFS
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Cf. A059045.
Cf. A027261, A064017, A079272.
Sequence in context: A000418 A055852 A122611 this_sequence A137747 A005023 A094256
Adjacent sequences: A014912 A014913 A014914 this_sequence A014916 A014917 A014918
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KEYWORD
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nonn,easy
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AUTHOR
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Olivier Gerard (olivier.gerard(AT)gmail.com)
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