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A330246
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a(n) = 4^(n+1) + (4^n-1)/3.
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2
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4, 17, 69, 277, 1109, 4437, 17749, 70997, 283989, 1135957, 4543829, 18175317, 72701269, 290805077, 1163220309, 4652881237, 18611524949, 74446099797, 297784399189, 1191137596757, 4764550387029, 19058201548117, 76232806192469, 304931224769877, 1219724899079509
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OFFSET
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0,1
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COMMENTS
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After 4, these numbers are the third column of the rectangular array in A238475.
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LINKS
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FORMULA
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G.f.: (4 - 3*x) / ((1 - x)*(1 - 4*x)).
a(n) = 5*a(n-1) - 4*a(n-2) for n > 1.
a(n) = 4*a(n-1) + 1 for n > 0.
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MATHEMATICA
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Table[(4^(n + 1) + (4^n - 1) / 3), {n, 0, 30}]
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PROG
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(Magma) [4^(n+1)+(4^n-1)/3: n in [0..30]];
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CROSSREFS
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Together with 1: first bisection of A136326.
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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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