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A137210
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Numbers k such that abundance(k) = abundance(sigma(k)).
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0
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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abundance(84) = sigma(84) - 2(84) = 56 = abundance(224) = abundance(sigma(84)), so 84 is a term in the sequence.
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MATHEMATICA
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abund[n_] := DivisorSigma[1, n]-2n; l = {}; For[i = 1, i <= 10^6, i++, If[abund[i] == abund[DivisorSigma[1, i]], l = Append[l, i]]]; l
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PROG
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(PARI) is(k) = {my(s = sigma(k)); s - 2*k == sigma(s) - 2*s; } \\ Amiram Eldar, Apr 06 2024
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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