Watermelon 3

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isAbundant[n_] :=
    Module[{sumDivisors},
        sumDivisors = Total[Divisors[n]] - n;
        sumDivisors > n]

abundantNumbers[a_, b_] :=
    Select[
        Range[a, b],
        isAbundant]

L := 28123

abundantList := abundantNumbers[1, L]

firstHalfAbundantList :=
    abundantNumbers[1, Quotient[L,2]]

abundantSums[aList_, bList_] :=
    DeleteDuplicates[
        Flatten[
            Table[
                aList[[i]] + bList[[j]],
                {i, Length[aList]},
                {j, Length[bList]}]]]

nonAbundantSums[limit_] :=
    Total[
        Complement[
            Range[1, limit],
            abundantSums[
                firstHalfAbundantList,
                abundantList]]]

result = Timing[nonAbundantSums[L]]

{1.73236, 4179871}

— Me@2024-10-20 01:49:38 PM

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2024.10.25 Friday (c) All rights reserved by ACHK