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A109895 Group the natural numbers so that every 2n-th group product is divisible by the single number in the next group. (1), (2,3,4,5), (6), (7,8,9,10,11), (12), (13,14,15,16,17,18,19),(20), (21,22,23,24,25,26,27),(28),... Sequence contains the single members of the odd numbered groups. 4

%I

%S 1,6,12,20,28,36,45,56,70,80,90,104,112,120,132,140,154,168,180,192,

%T 208,220,234,250,264,280,297,312,324,336,350,360,378,396,416,432,448,

%U 462,480,495,504,520,539,560,576,594,612,630,640,660,672,693,714,728,748

%N Group the natural numbers so that every 2n-th group product is divisible by the single number in the next group. (1), (2,3,4,5), (6), (7,8,9,10,11), (12), (13,14,15,16,17,18,19),(20), (21,22,23,24,25,26,27),(28),... Sequence contains the single members of the odd numbered groups.

%C a(n) divides (a(n)-1)! / (a(n-1)!) and is the smallest integer with this property. - Simon Nickerson (simonn(AT)maths.bham.ac.uk), Jul 15 2005

%C Essentially a duplicate of A079760. [From _R. J. Mathar_, Aug 18 2008]

%o (GAP) A := [ 1 ]; n := 1; repeat p := 1; k := n + 1; repeat p := p * k; k := k+1; until p mod k = 0; n := k; Add(A, n); until n > 10000; (Nickerson)

%Y Cf. A079759, A109896, A109897.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Jul 13 2005

%E More terms from Simon Nickerson (simonn(AT)maths.bham.ac.uk), Jul 15 2005

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Last modified April 10 15:07 EDT 2021. Contains 342845 sequences. (Running on oeis4.)