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A199978
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Nonprime numbers whose multiplicative digital root is 0.
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2
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10, 20, 25, 30, 40, 45, 50, 52, 54, 55, 56, 58, 60, 65, 69, 70, 78, 80, 85, 87, 90, 95, 96, 100, 102, 104, 105, 106, 108, 110, 120, 125, 130, 140, 145, 150, 152, 154, 155, 156, 158, 159, 160, 165, 169, 170, 178, 180, 185, 187, 190, 195, 196, 200, 201, 202
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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Number 58 is in sequence because 5*8 = 40, 4*0 = 0.
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MATHEMATICA
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digRoot[n_] := Module[{k = n}, While[k > 9, k = Times @@ IntegerDigits[k]]; k]; Select[Range[300], ! PrimeQ[#] && digRoot[#] == 0 &] (* T. D. Noe, Nov 23 2011 *)
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CROSSREFS
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Cf. A199977 (primes whose multiplicative digital root is 0).
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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