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A068584
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Numbers k such that the denominator of (Sum_{j=1..k} 1/j)^2 equals the denominator of Sum_{j=1..k} 1/j^2.
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1
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1, 2, 3, 4, 5, 9, 15, 16, 17, 28, 29, 30, 31, 32, 49, 91, 92, 93, 94, 95, 96, 97, 98, 99, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 243, 244, 245, 246, 247, 248, 249, 968, 969, 970, 971, 972, 973, 974, 975, 976, 977, 978, 979, 980, 981, 982, 983, 984
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OFFSET
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1,2
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LINKS
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FORMULA
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MATHEMATICA
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s = {}; sum1 = sum2 = 0; Do[sum1 += 1/j; sum2 += 1/j^2; If[Denominator[sum1^2] == Denominator[sum2], AppendTo[s, j]], {j, 1, 1000}]; s (* Amiram Eldar, Feb 18 2021 *)
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PROG
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(PARI) isok(k) = denominator(sum(j=1, k, 1/j)^2) == denominator(sum(j=1, k, 1/j^2)); \\ Michel Marcus, Feb 15 2021
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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