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A271329
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a(n) is the sum of the divisors of the n-th sphenic number (A007304).
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1
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72, 96, 144, 144, 168, 216, 192, 216, 240, 252, 288, 288, 288, 324, 360, 336, 384, 360, 336, 456, 432, 384, 432, 504, 432, 528, 480, 448, 576, 480, 504, 540, 576, 648, 576, 576, 720, 576, 744, 684, 648, 576, 640, 816, 720, 756, 720, 864, 672, 792, 768, 720
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 72 because the divisors of A007304(1) = 30 are {1,2,3,5,6,10,15,30}, the sum of which is 72.
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MATHEMATICA
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DivisorSigma[1, #]&/@With[{upto=500}, Sort[Select[Times@@@Subsets[ Prime[ Range[ Ceiling[ upto/6]]], {3}], #<=upto&]]] (* Harvey P. Dale, May 30 2020 *)
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PROG
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(PARI)
L=List(); for(n=1, 1000, if(bigomega(n)==3 && omega(n)==3, listput(L, sum(k=1, 8, divisors(n)[k])))); Vec(L)
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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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