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A134376
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Numbers whose sum of prime factors (counted with multiplicity) is not prime.
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26
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1, 4, 8, 9, 14, 15, 16, 18, 20, 21, 24, 25, 26, 27, 30, 32, 33, 35, 36, 38, 39, 42, 44, 46, 49, 50, 51, 55, 57, 60, 62, 64, 65, 66, 68, 69, 70, 72, 74, 77, 78, 81, 84, 85, 86, 87, 91, 92, 93, 94, 95, 98, 100, 102, 105, 106, 110, 111, 112, 114, 115, 116, 119, 120, 121, 122
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OFFSET
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1,2
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COMMENTS
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The first term is 1, since 1 has no prime factors and so the sum of prime factors evaluates to zero.
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LINKS
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EXAMPLE
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a(2) = 4, since 4 = 2*2 and 2+2 = 4 is not prime.
a(5) = 14, since 14 = 2*7 and 2+7 = 9 is not prime.
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MATHEMATICA
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Select[Range[150], !PrimeQ[Total[Flatten[Table[#[[1]], #[[2]]]&/@ FactorInteger[ #]]]]&] (* Harvey P. Dale, Jul 05 2021 *)
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PROG
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(PARI) sopfr(n)=my(f=factor(n)); sum(i=1, #f~, f[i, 1]*f[i, 2])
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CROSSREFS
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Cf. A000040, A001222, A100118, A046363, A133620, A133621, A133880, A133890, A133900, A133910, A133911, A046346, A134331, A134332, A134333, A134334, A134344, A078177.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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Edited by the author at the suggestion of T. D. Noe, May 20 2013
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STATUS
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approved
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