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 A104660 Number of distinct prime divisors of 44...443 (with n 4s). 2
 1, 1, 2, 2, 1, 3, 3, 1, 2, 2, 1, 2, 2, 3, 3, 3, 3, 3, 4, 3, 3, 6, 3, 4, 3, 3, 6, 4, 1, 5, 1, 4, 3, 5, 3, 6, 4, 2, 6, 2, 2, 3, 5, 3, 4, 4, 4, 2, 2, 4, 4, 3, 4, 5, 6, 3, 3, 5, 2, 4, 3, 5, 4, 4, 3, 6, 4, 3, 6, 6, 4, 5, 4, 2, 4, 5, 2, 4, 5, 6, 4, 4, 3, 6, 5, 4, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Amiram Eldar, Table of n, a(n) for n = 1..199 FORMULA a(n) = A001221(A173770(n+1)). - Amiram Eldar, Jan 25 2020 EXAMPLE The number of distinct prime divisors of 43 is 1 (prime). The number of distinct prime divisors of 443 is 1 (prime). The number of distinct prime divisors of 4443 is 2. MAPLE A104660 := proc(n) x := [3, seq(4, k=1..n)] ; add(op(i, x)*10^(i-1), i=1..nops(x)) ; numtheory[factorset](%) ; nops(%) ; end proc: seq(A104660(n), n=1..45) ; # R. J. Mathar, Aug 23 2011 MATHEMATICA Table[PrimeNu[FromDigits[Join[Table[4, {n}], {3}]]], {n, 50}] (* Alonso del Arte, Aug 23 2011 *) Table[PrimeNu[FromDigits[PadLeft[{3}, n, 4]]], {n, 2, 70}] (* Harvey P. Dale, Aug 22 2016 *) CROSSREFS Cf. A001221, A104518, A173770. Sequence in context: A104469 A144112 A178568 * A212125 A282936 A220073 Adjacent sequences:  A104657 A104658 A104659 * A104661 A104662 A104663 KEYWORD nonn,base AUTHOR Parthasarathy Nambi, Apr 21 2005 EXTENSIONS More terms from R. J. Mathar and Alonso del Arte, Aug 23 2011 More terms from Amiram Eldar, Jan 25 2020 STATUS approved

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Last modified June 22 21:29 EDT 2021. Contains 345393 sequences. (Running on oeis4.)