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A152864
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Deficiency of n, plus the number of proper divisors of n: a(n) = 2n - sigma(n) + d(n) - 1.
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4
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1, 2, 3, 3, 5, 3, 7, 4, 7, 5, 11, 1, 13, 7, 9, 5, 17, 2, 19, 3, 13, 11, 23, -5, 21, 13, 17, 5, 29, -5, 31, 6, 21, 17, 25, -11, 37, 19, 25, -3, 41, -5, 43, 9, 17, 23, 47, -19, 43, 12, 33, 11, 53, -5, 41, -1, 37, 29, 59, -37, 61, 31
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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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a[n_] := 2*n - Differences[DivisorSigma[{0, 1}, n]][[1]] - 1; Array[a, 100] (* Amiram Eldar, Apr 07 2024 *)
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PROG
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(PARI) a(n) = 2*n - sigma(n) + numdiv(n) - 1; \\ Amiram Eldar, Apr 07 2024
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CROSSREFS
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KEYWORD
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easy,sign
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AUTHOR
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STATUS
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approved
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