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A104518
Number of distinct prime divisors of 55...3 (with n 5s).
4
1, 2, 2, 2, 2, 2, 1, 3, 2, 2, 3, 4, 3, 3, 4, 2, 2, 4, 3, 3, 5, 2, 2, 6, 1, 3, 4, 5, 7, 4, 4, 3, 6, 4, 4, 7, 5, 6, 4, 3, 3, 5, 2, 4, 6, 4, 5, 6, 4, 4, 4, 5, 4, 4, 4, 5, 4, 3, 2, 5, 3, 3, 3, 3, 1, 5, 7, 6, 2, 3, 5, 3, 1, 7, 2, 4, 3, 8, 4, 6, 3, 3, 3, 6, 5, 3, 5
OFFSET
1,2
LINKS
FORMULA
a(n) = A001221(A173802(n+1)). - R. J. Mathar, Aug 24 2011
EXAMPLE
The number of distinct prime divisors of 53 is 1 (prime) which is the first term in the sequence.
The number of distinct prime divisors of 553 is 2 which is the second term in the sequence.
The number of distinct prime divisors of 5553 is 2 which is the third term in the sequence.
MAPLE
A104518 := proc(n) local x ; x := [3, seq(5, k=1..n)] ; add(op(i, x)*10^(i-1), i=1..nops(x)) ; numtheory[factorset](%) ; nops(%) ; end proc: # R. J. Mathar, Aug 24 2011
MATHEMATICA
Table[PrimeNu[(50*10^n - 23)/9], {n, 0, 50}] (* G. C. Greubel, May 06 2017 *)
CROSSREFS
Sequence in context: A271778 A326702 A133563 * A329030 A027388 A114295
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Apr 19 2005
EXTENSIONS
More terms from Amiram Eldar, Jan 25 2020
STATUS
approved