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A054611
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a(n) = Sum_{d|n} phi(d)*4^(n/d).
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6
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0, 4, 20, 72, 280, 1040, 4200, 16408, 65840, 262296, 1049680, 4194344, 16782000, 67108912, 268451960, 1073744160, 4295033440, 17179869248, 68719747320, 274877907016, 1099512679520, 4398046544304, 17592190238920, 70368744177752
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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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MAPLE
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A054611:=proc(n) local k, t1; t1:=0; for k in divisors(n) do t1 := t1+phi(k)*4^(n/k); od: t1; end;
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PROG
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(PARI) a(n) = if(n==0, 0, sumdiv(n, d, eulerphi(d)*4^(n/d))); \\ Michel Marcus, Sep 19 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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