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 A067340 Numbers k such that (number of distinct prime factors of k) divides (number of prime factors of k). 12
 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 21, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 46, 47, 49, 51, 53, 54, 55, 56, 57, 58, 59, 61, 62, 64, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 81, 82, 83, 85, 86, 87, 88, 89, 91 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Stanislav Sykora, Table of n, a(n) for n = 1..20000 FORMULA A001222(k)/A001221(k) is an integer. EXAMPLE Primes and prime powers are included in this sequence. Another example: 24, since A001222(24)/A001222(24) = 4/2 = 2. MATHEMATICA ff[x_] := Flatten[FactorInteger[x]]; f1[x_] := Length[FactorInteger[x]]; f2[x_] := Apply[Plus, Table[Part[ff[x], 2*w], {w, 1, f1[x]}]]; Do[s=f2[n]/f1[n]; If[IntegerQ[s], Print[n]], {n, 2, 256}] Select[Range[2, 91], Divisible[PrimeOmega[#], PrimeNu[#]]&] (* Ivan N. Ianakiev, Dec 07 2015 *) PROG (PARI) v=[]; for(n=2, 100, if(denominator(bigomega(n)/omega(n)) == 1, v=concat(v, n))); v (PARI) is(n)=my(f=factor(n)[, 2]); #f && vecsum(f)%#f==0 \\ Charles R Greathouse IV, Oct 15 2015 CROSSREFS Cf. A001221, A001222, A245080. Sequence in context: A107909 A255724 A285100 * A263837 A283550 A271113 Adjacent sequences:  A067337 A067338 A067339 * A067341 A067342 A067343 KEYWORD nonn AUTHOR Labos Elemer, Jan 16 2002 STATUS approved

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Last modified January 22 23:00 EST 2019. Contains 319365 sequences. (Running on oeis4.)