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A367553
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a(n) = Sum_{d|n} (d+n/d)^n.
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0
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2, 18, 128, 1506, 15552, 266548, 4194304, 89452674, 2010077696, 52439799700, 1486016741376, 46761291772836, 1587429546508288, 58431605635691172, 2305913377957871616, 97342665226310447618, 4371823119477393063936, 208266120619720061526886
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OFFSET
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1,1
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COMMENTS
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a(n) is even.
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LINKS
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FORMULA
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a(n) = Sum_{k=0..n} n^(n-k) * binomial(n,k) * (Sum_{d|n} d^(2*k-n)) = Sum_{k=0..n} binomial(n,k) * (Sum_{d|n} d^k * (n/d)^(n-k)).
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PROG
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(PARI) a(n) = sumdiv(n, d, (d+n/d)^n);
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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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