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A072073
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Number of solutions to Cototient(x) = A051953(x) = 2^n.
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0
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1, 2, 3, 3, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10
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OFFSET
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1,2
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COMMENTS
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Since A051953(p) = 1 for p prime, and given that there are an infinite number of primes, we disregard a(0) = oo. - Michael De Vlieger, Mar 25 2020
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LINKS
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EXAMPLE
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InvCototient(2^0) has an infinite number of entries, so 2^0=1 is left out.
n=14: 2^14=16384, InvCototient(16384) = {24576,28672,31744,32512,32764,32768}, so a(14)=6;
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MATHEMATICA
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Length /@ Most@ Split@ DeleteCases[Select[Array[# - EulerPhi[#] &, 10^6], IntegerQ@ Log2@ # &], 1] (* Michael De Vlieger, Mar 25 2020 *)
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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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