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A053193
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Cototient of odd numbers.
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5
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1, 1, 1, 3, 1, 1, 7, 1, 1, 9, 1, 5, 9, 1, 1, 13, 11, 1, 15, 1, 1, 21, 1, 7, 19, 1, 15, 21, 1, 1, 27, 17, 1, 25, 1, 1, 35, 17, 1, 27, 1, 21, 31, 1, 19, 33, 23, 1, 39, 1, 1, 57, 1, 1, 39, 1, 27, 45, 23, 11, 43, 25, 1, 45, 1, 25, 63, 1, 1, 49, 23, 33, 63, 1, 1, 57, 35, 1, 55, 29, 1, 85, 1, 13
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OFFSET
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1,4
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LINKS
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FORMULA
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a(n) = cototient(2n+1) = A051953(2n+1).
Sum_{k=1..n} a(k) ~ c * n^2, where c = 1 - 8/Pi^2. - Amiram Eldar, Dec 15 2023
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EXAMPLE
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n=12, 2n+1=25, phi(25)=20, cototient(25)=25-20=5, a(12)=5.
n=16, 2n+1=33, phi(33)=20, cototient(33)=33-20=13, a(16)=13.
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MATHEMATICA
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PROG
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CROSSREFS
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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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