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A125049
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a(1) = 1. If a(n) is prime, a(n+1) = 2*a(n); otherwise, a(n+1) = 2*a(n) + 1.
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1
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1, 3, 6, 13, 26, 53, 106, 213, 427, 855, 1711, 3423, 6847, 13695, 27391, 54783, 109567, 219134, 438269, 876539, 1753079, 3506159, 7012318, 14024637, 28049275, 56098551, 112197103, 224394207, 448788415, 897576831, 1795153663, 3590307326
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OFFSET
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1,2
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LINKS
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FORMULA
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MAPLE
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a := proc(n)
local c, k:
c, k := 1, 1:
while c < n do
if isprime(k) then k := 2*k: else k := 2*k+1: fi:
c := c+1: od:
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MATHEMATICA
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NestList[If[PrimeQ[#], 2#, 2#+1]&, 1, 40] (* Harvey P. Dale, Sep 01 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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