

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
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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 primepower.  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), 437446.
Index entries for sequences related to EKG sequence


FORMULA

a(n) = gcd(A064413(n1), 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 !! (n2)
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



