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 A058062 Number of distinct prime factors of sigma(n), the sum of the divisors of n. 2
 0, 1, 1, 1, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 3, 1, 2, 2, 3, 1, 3, 2, 2, 3, 2, 1, 2, 2, 2, 2, 2, 2, 3, 2, 3, 3, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 3, 3, 2, 2, 2, 1, 3, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 1, 3, 3, 2, 2, 3, 3, 3, 3, 3, 2, 3, 1, 2, 3, 3, 2, 2, 3, 2, 3, 2, 2, 4, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS G. C. Greubel, Table of n, a(n) for n = 0..5000 FORMULA a(n) = A001221(A000203(n)). EXAMPLE n=81, sigma(81) = 81+27+9+3+1 = 121 = 11^2, so a(81) = 1. MATHEMATICA Table[PrimeNu[DivisorSigma[1, n]], {n, 50}] (* G. C. Greubel, May 20 2017 *) PROG (PARI) for(n=1, 50, print1(omega(sigma(n)), ", ")) \\ G. C. Greubel, May 20 2017 CROSSREFS Cf. A001221, A000203. Sequence in context: A091267 A003643 A092788 * A102820 A024317 A024880 Adjacent sequences:  A058059 A058060 A058061 * A058063 A058064 A058065 KEYWORD nonn AUTHOR Labos Elemer, Nov 23 2000 STATUS approved

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Last modified January 27 09:09 EST 2020. Contains 331293 sequences. (Running on oeis4.)