%I A090904
%S A090904 1,2,12,1680,2162160,4626053752320000,13644281345408020027550269440000,
%T A090904 4402827357584746886229433170489943024971625310770489684257669120000000000
%N A090904 Group the natural numbers so that the n-th group product is a multiple 
               of the (n-1)th group product. (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),... Sequence contains 
               the product of terms of the groups.
%C A090904 Conjecture: For n > 4 the last term of the n-th group is 2p where p is 
               the largest prime in the (n-1)th group. And these are the Bertrand 
               primes.
%Y A090904 Cf. A090905, A090906, A090907.
%Y A090904 Sequence in context: A111180 A085912 A085895 this_sequence A125295 A050649 
               A003042
%Y A090904 Adjacent sequences: A090901 A090902 A090903 this_sequence A090905 A090906 
               A090907
%K A090904 nonn
%O A090904 1,2
%A A090904 Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Dec 13 2003
%E A090904 More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Feb 10 
               2006