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A073734 GCD of consecutive members of the EKG sequence A064413. 5
1, 2, 2, 3, 3, 3, 4, 2, 5, 5, 3, 2, 7, 7, 3, 8, 4, 2, 11, 11, 3, 3, 5, 5, 7, 2, 13, 13, 3, 4, 2, 17, 17, 3, 2, 19, 19, 3, 5, 4, 2, 23, 23, 3, 2, 2, 2, 2, 7, 7, 3, 5, 5, 5, 2, 29, 29, 3, 2, 31, 31, 3, 8, 4, 2, 37, 37, 3, 3, 2, 4, 2, 41, 41, 3, 3, 7, 11, 2, 43, 43, 3, 5, 5, 5, 4, 2, 47, 47, 3, 2, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

All terms shown are prime powers, but this does not hold for all n. For n > 2, a(n) is divisible by A064740(n).

The GCD of A064413(578)=620 and A064413(579)=610 is 10. This is the first time the GCD is not a prime-power. - N. J. A. Sloane, Mar 30 2015

a(A064955(n)) = A000040(n) for n > 1. [Reinhard Zumkeller, Sep 17 2001]

LINKS

T. D. Noe, Table of n, a(n) for n=2..1000

J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446.

Index entries for sequences related to EKG sequence

FORMULA

a(n) = gcd(A064413(n-1), A064413(n)).

EXAMPLE

a(8) = 4 because gcd(A064413(7), A064413(8)) = gcd(12, 8) = 4.

MATHEMATICA

t = {1, 2}; Join[{1}, Table[k = 3; While[MemberQ[t, k] || (y = GCD[Last[t], k]) == 1, k++]; AppendTo[t, k]; y, {91}]] (* Jayanta Basu, Jul 09 2013 *)

PROG

(Haskell)

a073734 n = a073734_list !! (n-2)

a073734_list = zipWith gcd a064413_list $ tail a064413_list

-- Reinhard Zumkeller, Sep 17 2001

CROSSREFS

Cf. A064413, A064740, A073735.

Sequence in context: A051776 A270920 A262956 * A231335 A271237 A062558

Adjacent sequences:  A073731 A073732 A073733 * A073735 A073736 A073737

KEYWORD

easy,nonn

AUTHOR

David Wasserman, Aug 06 2002

STATUS

approved

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Last modified September 26 20:36 EDT 2020. Contains 337374 sequences. (Running on oeis4.)