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A159886
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Values k such that sigma(x) = k has more than one solution, sigma = A000203.
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8
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12, 18, 24, 31, 32, 42, 48, 54, 56, 60, 72, 80, 84, 90, 96, 98, 104, 108, 114, 120, 124, 126, 128, 132, 140, 144, 152, 156, 168, 180, 182, 186, 192, 210, 216, 224, 228, 234, 240, 248, 252, 264, 270, 272, 280, 288, 294, 308, 312, 320, 324, 336, 342, 360, 372, 378, 384, 390
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OFFSET
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1,1
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COMMENTS
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Numbers k with A054973(k) >= 2. Numbers k which occur in A000203 more than once.
See A300869 for the odd terms, much less frequent since they can only occur for x = k^2 or 2*k^2. - M. F. Hasler, Mar 16 2018
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LINKS
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EXAMPLE
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a(1)=12 as the multiplicity of the value 12 is 2: 12 = sigma(6) = sigma(11).
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PROG
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(PARI)
na(n) = local(v, s); v=vector(n); for(k=1, n, s=sigma(k); if(s<=n, v[s]++)); v
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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