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A086224
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a(n) = 7*2^n - 1.
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20
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6, 13, 27, 55, 111, 223, 447, 895, 1791, 3583, 7167, 14335, 28671, 57343, 114687, 229375, 458751, 917503, 1835007, 3670015, 7340031, 14680063, 29360127, 58720255, 117440511, 234881023, 469762047, 939524095, 1879048191, 3758096383
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OFFSET
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0,1
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COMMENTS
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Let A be the Hessenberg matrix of order n, defined by: A[1,j]=1, A[i,i]:=-3, A[i,i-1]=-1, and A[i,j]=0 otherwise. Then, for n>=1, a(n-1)=(-1)^n*charpoly(A,-5). - Milan Janjic, Jan 27 2010
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LINKS
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FORMULA
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a(n+1) = 2*a(n) + 1.
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MATHEMATICA
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PROG
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CROSSREFS
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Other sequences with recurrence a(n+1) = 2*a(n) + 1 are:
a(0) = 7 gives essentially A000225.
a(0) = 8 gives A052996 except for some initial terms,
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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