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A054610
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a(n) = Sum_{d|n} phi(d)*3^(n/d).
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7
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0, 3, 12, 33, 96, 255, 780, 2205, 6672, 19755, 59340, 177177, 532416, 1594359, 4785228, 14349525, 43053504, 129140211, 387441756, 1162261521, 3486844320, 10460357775, 31381236876, 94143178893, 282430082832, 847288610475
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = Sum_{k=1..n} 3^(n/gcd(n,k))*phi(gcd(n,k))/phi(n/gcd(n,k)). - Richard L. Ollerton, May 07 2021
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PROG
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(PARI) a(n) = sum(k=1, n, 3^gcd(n, k)); \\ Michel Marcus, Apr 16 2021
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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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