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A015487
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a(0)=1, a(1)=3, a(n) = sum_{k=0}^{k=n-1} 3^k a(k).
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0
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1, 3, 10, 100, 2800, 229600, 56022400, 40896352000, 89481218176000, 587175753670912000, 11557967535258231808000, 682497982956998588262400000, 120903152684866385913507635200000
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OFFSET
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0,2
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LINKS
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FORMULA
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PROG
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(Magma) I:=[1, 3, 10]; [n le 3 select I[n] else (3^(n-2)+1)*Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 10 2012
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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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