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A045661
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a(n) = Product_{d|n} (n/d + d).
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1
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2, 9, 16, 100, 36, 1225, 64, 2916, 600, 5929, 144, 529984, 196, 18225, 16384, 231200, 324, 3538161, 400, 5143824, 48400, 89401, 576, 1482250000, 6760, 164025, 112896, 26050816, 900, 5679280321, 1024, 50808384, 226576, 442225
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OFFSET
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1,1
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COMMENTS
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a(n) is a square when n is not a square or of the form (2m^2)^2 = 4m^4.
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LINKS
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FORMULA
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MATHEMATICA
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Times@@(#/Divisors[ # ]+Divisors[ # ])& /@ Range[ 48 ]
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PROG
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(Haskell)
a045661 n = product [n'+d | d <- [1..n], let (n', m) = divMod n d, m == 0]
(PARI) A045661(n)=my(t=1+#n=divisors(n)); prod(i=1, (t-1)\2, n[i]+n[t-i])^2*if(bittest(t, 0), 1, 2*n[t\2]) \\ M. F. Hasler, Jan 25 2012
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CROSSREFS
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KEYWORD
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nonn,nice,easy
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AUTHOR
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STATUS
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approved
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