A109897 - OEIS

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.

%I #8 Nov 04 2018 13:14:09

%S 120,55440,253955520,4475671200,33891580800,7146019520640,

%T 106137499051584000,240679032790296606105600,74684882115043200,

%U 230656425830328960,66654064122818055916032000,171176782669200,282328002094320,126639913316232476160000,859891329773280

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

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

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

%Y Cf. A079759, A109895, A109896.

%K nonn

%O 1,1

%A _Amarnath Murthy_, Jul 13 2005

%E Terms from a(5) from _Franklin T. Adams-Watters_, Jun 26 2011