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A087021 Number of distinct prime factors of n-th 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 (list; graph; refs; listen; history; text; internal format)
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, A087021-A087026.

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

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Last modified November 21 14:18 EST 2019. Contains 329371 sequences. (Running on oeis4.)