A015508 revision #5
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A015508
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a(1)=1, a(n) = sum_{k=1}^{k=n-1} (7^k-1)/6 a(k).
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10
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1, 1, 9, 522, 209322, 586520244, 11501075464596, 1578614616119517768, 1516734501782248791012168, 10200952598655696033329019125136, 480252779391204632593567857157274897424, 158269444415262012661462389451687149577571916192
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OFFSET
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1,3
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LINKS
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FORMULA
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PROG
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(MAGMA) I:=[1, 1, 9]; [n le 3 select I[n] else ((7^(n-1) + 5)/6) * Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 12 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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editing
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