A109895


Group the natural numbers so that every 2nth 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 2nth 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(n1)!) 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
