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A113594 a(1) = a(2) = 1; a(n+1) = GCD(sum_{1<=k<=n/2} a(k), sum_{n/2<j<=n} a(j)). 0
1, 1, 1, 1, 2, 2, 1, 3, 4, 4, 2, 2, 8, 8, 1, 1, 6, 12, 4, 16, 20, 20, 2, 2, 4, 8, 8, 16, 40, 40, 1, 1, 2, 2, 6, 12, 12, 12, 32, 64, 16, 80, 20, 100, 120, 120, 2, 2, 4, 4, 4, 8, 8, 8, 16, 16, 16, 32, 40, 200, 240, 240, 1, 1, 2, 2, 2, 4, 6, 6, 12, 12, 24, 24, 12, 12, 72, 144, 32, 64, 192, 384 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

a(2n-1) divides a(2n), for every positive integer n.

LINKS

Table of n, a(n) for n=1..82.

EXAMPLE

a(12) = GCD(a(1)+a(2)+a(3)+a(4)+a(5), a(6)+a(7)+a(8)+a(9)+a(10)+a(11)) =

GCD(1+1+1+1+2, 2+1+3+4+4+2) = GCD(6,16) = 2.

MATHEMATICA

a[1] = a[2] = 1; a[n_] := a[n] = GCD[ Sum[a[k], {k, Floor[(n - 1)/2]}], Sum[a[j], {j, Ceiling[n/2], n - 1}]]; Array[a, 82] (* Robert G. Wilson v *)

CROSSREFS

Sequence in context: A193820 A216368 A123956 * A246425 A286468 A102563

Adjacent sequences:  A113591 A113592 A113593 * A113595 A113596 A113597

KEYWORD

nonn

AUTHOR

Leroy Quet, Jan 26 2006

EXTENSIONS

More terms from Robert G. Wilson v, Feb 01 2006

STATUS

approved

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Last modified May 23 07:08 EDT 2019. Contains 323508 sequences. (Running on oeis4.)