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 A050690 Sum of digits of zero-absent composite a(n) equals number of prime factors. 2
 12, 32, 1152, 11232, 13122, 14112, 21312, 111132, 112112, 3121152, 11231232, 11354112, 812122112, 1251213312, 2211121152, 2211213312, 5121114112, 26122125312, 56321114112, 62214111232, 431711322112, 3421411213312, 11111212122112, 11112113242112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 10^11 < a(21) <= 431711322112. a(22) <= 3421411213312. - Donovan Johnson, May 30 2010 LINKS Table of n, a(n) for n=1..24. EXAMPLE 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. MATHEMATICA 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 *) CROSSREFS Cf. A050689, A057531, A057532, A070274, A070275, A063737, A067077. Sequence in context: A045660 A334307 A192213 * A079561 A328326 A131543 Adjacent sequences: A050687 A050688 A050689 * A050691 A050692 A050693 KEYWORD nonn,base,nice,hard AUTHOR Patrick De Geest, Aug 15 1999 EXTENSIONS a(15)-a(20) from Donovan Johnson, May 30 2010 a(21)-a(22) confirmed by Giovanni Resta, Jun 02 2013 a(23)-a(24) from Giovanni Resta, Apr 23 2017 STATUS approved

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Last modified September 22 11:32 EDT 2023. Contains 365531 sequences. (Running on oeis4.)