

A087021


Number of distinct prime factors of nth cyclic number.


3



4, 8, 9, 8, 10, 8, 10, 21, 23, 19, 19, 15, 16, 12, 11, 33, 31, 19, 24, 22, 24, 18, 14, 33, 39, 23, 36, 13, 13, 19, 36, 32, 29, 27, 25, 11, 20, 56, 37, 46, 25, 22
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OFFSET

1,1


COMMENTS

A004042(n) factorized with Dario Alpern's ECM.
Extended using factors of 10^(A001913(n)1)1, see Kamada link.


LINKS

Table of n, a(n) for n=1..42.
Dario A. Alpern, Factorization using the Elliptic Curve Method.
Makoto Kamada, Factorizations of 11...11 (Repunit)
Eric Weisstein's World of Mathematics, Cyclic Number


FORMULA

a(n) = A001221(A004042(n+1)).


EXAMPLE

A004042(2) = 142857 = 37*13*11*3^3, therefore a(1) =
#{3,11,13,37} = 4.


CROSSREFS

Cf. A001913, A087021A087026.
Sequence in context: A200634 A154177 A010480 * A163409 A312828 A267647
Adjacent sequences: A087018 A087019 A087020 * A087022 A087023 A087024


KEYWORD

nonn,more,hard


AUTHOR

Reinhard Zumkeller, Jul 30 2003


EXTENSIONS

a(3) corrected, a(12)a(42) added by Ray Chandler, Nov 16 2011


STATUS

approved



