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 A033273 Number of nonprime divisors of n. 25
 1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 4, 1, 2, 2, 4, 1, 4, 1, 4, 2, 2, 1, 6, 2, 2, 3, 4, 1, 5, 1, 5, 2, 2, 2, 7, 1, 2, 2, 6, 1, 5, 1, 4, 4, 2, 1, 8, 2, 4, 2, 4, 1, 6, 2, 6, 2, 2, 1, 9, 1, 2, 4, 6, 2, 5, 1, 4, 2, 5, 1, 10, 1, 2, 4, 4, 2, 5, 1, 8, 4, 2, 1, 9, 2, 2, 2, 6, 1, 9, 2, 4, 2, 2, 2, 10, 1, 4, 4, 7, 1, 5, 1, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS a(A055079(n)) = n and a(m) <> n for m < A055079(n). - Reinhard Zumkeller, Dec 16 2013 LINKS Ray Chandler, Table of n, a(n) for n=1..100000 FORMULA a(n) = A000005(n) - A001221(n). G.f.: Sum_{k>=1} (x^k - x^prime(k))/((1 - x^k)*(1 - x^prime(k))). - Ilya Gutkovskiy, Jan 17 2017 Dirichlet g.f.: zeta(s)*(zeta(s)-primezeta(s)). - Benedict W. J. Irwin, Jul 11 2018 MATHEMATICA Table[Length[Select[Divisors[n], ! PrimeQ[#] &]], {n, 104}] (* Jayanta Basu, May 23 2013 *) Table[DivisorSigma[0, n] - PrimeNu[n], {n, 100}] (* Vincenzo Librandi, May 17 2017 *) Table[Count[Divisors[n], _?CompositeQ], {n, 110}]+1 (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 11 2019 *) PROG (Haskell) a033273 = length . filter ((== 0) . a010051) . a027750_row -- Reinhard Zumkeller, Dec 16 2013 (PARI) a(n) = numdiv(n) - omega(n); \\ Michel Marcus, Apr 28 2016 (MAGMA) [NumberOfDivisors(n) - #PrimeDivisors(n): n in [1..150]]; // Vincenzo Librandi, May 17 2017 CROSSREFS Cf. A000005, A001221. Cf. A059992, A180040. Cf. A010051, A027750. Sequence in context: A294894 A076526 A226378 * A319685 A034836 A316365 Adjacent sequences:  A033270 A033271 A033272 * A033274 A033275 A033276 KEYWORD nonn AUTHOR EXTENSIONS More terms from Reinhard Zumkeller, Sep 02 2003 Corrected error in offset. - Jaroslav Krizek, May 04 2009 Extended by Ray Chandler, Aug 07 2010 STATUS approved

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Last modified February 17 18:14 EST 2020. Contains 332005 sequences. (Running on oeis4.)