A109897 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 product of terms in the 2n-th group.

120, 55440, 253955520, 4475671200, 33891580800, 7146019520640, 106137499051584000, 240679032790296606105600, 74684882115043200, 230656425830328960, 66654064122818055916032000, 171176782669200, 282328002094320, 126639913316232476160000, 859891329773280

Offset: 1

Author

Amarnath Murthy, Jul 13 2005

Keywords

• nonn

Examples

			a(2) = 7*8*9*10*11 = 55440.
		

Crossrefs

Cf. A079759, A109895, A109896.

Programs

PARI

m=1;for(k=2,150,if(m%k==0,print1(m", ");m=1,m*=k))

Extensions

Terms from a(5) from Franklin T. Adams-Watters, Jun 26 2011