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A099978
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Bisection of A001157: a(n) = sigma_2(2n-1).
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2
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1, 10, 26, 50, 91, 122, 170, 260, 290, 362, 500, 530, 651, 820, 842, 962, 1220, 1300, 1370, 1700, 1682, 1850, 2366, 2210, 2451, 2900, 2810, 3172, 3620, 3482, 3722, 4550, 4420, 4490, 5300, 5042, 5330, 6510, 6100, 6242, 7381, 6890, 7540, 8420, 7922, 8500
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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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EXAMPLE
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a(1) = sigma_2(2*1-1) = 1.
a(2) = sigma_2(2*2-1) = 1 + 3^2 = 10.
a(5) = sigma_2(2*5-1) = 1 + 3^2 + 9^2 = 91. (End)
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MAPLE
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with(numtheory): A099978 := n->sigma[2](2*n-1): seq(A099978(n), n=1..60);
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MATHEMATICA
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DivisorSigma[2, Range[1, 91, 2]] (* Amiram Eldar, Aug 17 2019 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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