A087020 Greatest prime factor of n-th cyclic number.

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

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

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

Formula

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

Example

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

Crossrefs

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

Sequence in context: A262646 A063681 A289820 * A238840 A345467 A329226

Adjacent sequences: A087017 A087018 A087019 * A087021 A087022 A087023

Keyword

nonn

Author

Reinhard Zumkeller, Jul 30 2003

Extensions

a(12) from Ray Chandler, Nov 16 2011

Status

approved