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A072077
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Number of even nontotients not exceeding 2^n.
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2
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0, 0, 0, 1, 2, 6, 17, 41, 94, 215, 470, 1004, 2126, 4449, 9278, 19177, 39388, 80698, 164808, 335809, 683117, 1387415, 2813664, 5700228, 11536241, 23324624, 47122764, 95134678, 191937316, 387024829, 780018815, 1571331010
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OFFSET
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1,5
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LINKS
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EXAMPLE
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n = 6: a(6) = 6 because the even nontotients not exceeding 64 are {14,26,34,38,50,62}.
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MATHEMATICA
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a = Table[0, {2^26}]; Do[ b = EulerPhi[n]; If[ EvenQ[b] && b < 2^27, a[[b/2]]++ ], {n, 3, 10^9}]; c = 0; k = 1; Do[ While[k <= 2^n, If[ a[[k]] == 0, c++ ]; k++ ]; Print[c], {n, 1, 17}]
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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