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A084241
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a(n) = -5*a(n-1)-4*a(n-2) with n>1, a(0)=0, a(1)=1.
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2
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0, 1, -5, 21, -85, 341, -1365, 5461, -21845, 87381, -349525, 1398101, -5592405, 22369621, -89478485, 357913941, -1431655765, 5726623061, -22906492245, 91625968981, -366503875925, 1466015503701, -5864062014805, 23456248059221, -93824992236885
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OFFSET
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0,3
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COMMENTS
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abs(a(n))=A002450(n)=A001045(2n).
Binomial transform is (0,1,-3,9,-27,...).
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LINKS
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Table of n, a(n) for n=0..24.
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FORMULA
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a(n) = ((-1)^n-(-4)^n)/3.
a(n) = sum(k=1..n, (-1)^(n+k)*binomial(n, k)(-3)^(k-1)).
G.f.: x/((1+x)*(1+4*x)).
E.g.f.: (exp(-x)-exp(-4x))/3.
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CROSSREFS
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Apart from signs, identical to A002450.
Cf. A084240.
Sequence in context: A002054 A028948 A002450 * A187063 A026855 A097113
Adjacent sequences: A084238 A084239 A084240 * A084242 A084243 A084244
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KEYWORD
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sign,easy
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AUTHOR
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Paul Barry, May 21 2003
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STATUS
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approved
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