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A050690
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Sum of digits of zero-absent composite a(n) equals number of prime factors.
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2
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12, 32, 1152, 11232, 13122, 14112, 21312, 111132, 112112, 3121152, 11231232, 11354112, 812122112, 1251213312, 2211121152, 2211213312, 5121114112, 26122125312, 56321114112, 62214111232, 431711322112, 3421411213312, 11111212122112, 11112113242112
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OFFSET
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1,1
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COMMENTS
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10^11 < a(21) <= 431711322112. a(22) <= 3421411213312. - Donovan Johnson, May 30 2010
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LINKS
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EXAMPLE
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E.g., 21312 (no zero in the string) gives 2+1+3+1+2 = 9 prime factors, namely, 2*2*2*2*2*2*3*3*37.
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MATHEMATICA
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t={}; Do[If[FreeQ[x=IntegerDigits[n], 0]&&PrimeOmega[n]==Total[x], AppendTo[t, n]], {n, 2, 3220000, 2}]; t (* Jayanta Basu, May 30 2013 *)
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CROSSREFS
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KEYWORD
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nonn,base,nice,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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