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A366639
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a(n) = phi(7^n+1), where phi is Euler's totient function (A000010).
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10
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1, 4, 20, 168, 1200, 7600, 43200, 407680, 2712832, 19707408, 112560000, 945677920, 6768230400, 47530457728, 271289229120, 2096760960000, 16569393144832, 116315256993600, 597938524646400, 5699431359135360, 38890647857280000, 270061302781670400
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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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MATHEMATICA
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PROG
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(PARI) {a(n) = eulerphi(7^n+1)}
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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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