A286567 - OEIS

A286567

Smallest prime factor of the n-th Jacobsthal number: a(n) = A020639(A001045(n)), with a(1)=a(2)=1.

1, 1, 3, 5, 11, 3, 43, 5, 3, 11, 683, 3, 2731, 43, 3, 5, 43691, 3, 174763, 5, 3, 23, 2796203, 3, 11, 2731, 3, 5, 59, 3, 715827883, 5, 3, 43691, 11, 3, 1777, 174763, 3, 5, 83, 3, 2932031007403, 5, 3, 47, 283, 3, 43, 11, 3, 5, 107, 3, 11, 5, 3, 59, 2833, 3, 768614336404564651, 715827883, 3, 5, 11, 3, 7327657, 5, 3, 11, 56409643, 3, 1753, 223, 3, 5, 43, 3

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OFFSET

1,3

LINKS

Hans Havermann, Table of n, a(n) for n = 1..1122

FORMULA

a(n) = A020639(A001045(n)).

MATHEMATICA

Rest[FactorInteger[#][[1, 1]]&/@LinearRecurrence[{1, 2}, {0, 1}, 100]] (* Harvey P. Dale, Sep 23 2018 *)

PROG

(Scheme) (define (A286567 n) (A020639 (A001045 n)))

CROSSREFS