A087020 Greatest prime factor of n-th cyclic number.

37, 5882353, 333667, 513239, 121499449, 11111111111111111111111, 154083204930662557781201849, 39526741, 9999999900000001, 59779577156334533866654838281, 119968369144846370226083377, 8396862596258693901610602298557167100076327481

Offset: 1

Author

Reinhard Zumkeller, Jul 30 2003

Keywords

• nonn

Comments

A004042(n) factorized with Dario Alpern's ECM.

Extended using factors of 10^(A001913(n)-1)-1, see Kamada link.

Examples

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

Links

• Max Alekseyev, Table of n, a(n) for n = 1..51 (first 42 terms from Ray Chandler)
• Dario A. Alpern, Factorization using the Elliptic Curve Method.
• Makoto Kamada, Factorizations of 11...11 (Repunit)
• Eric Weisstein's World of Mathematics, Cyclic Number

Crossrefs

Cf. A001913, A087021, A087022, A087023, A087024, A087025, A087026.

Formula

a(n) = A006530(A004042(n+1)).

Extensions

a(12) from Ray Chandler, Nov 16 2011