OFFSET
1,1
COMMENTS
The n-th group is chosen so that it is lexicographically earliest.
First n-2 numbers are the least previously unused numbers.
The (n-1)st number is chosen with the additional condition that if the product is odd, the sum is also odd (to avoid an impossible situation in picking the n-th number).
The n-th number is chosen as the least unused number that meets the two prime conditions.
In the 3rd group, 6 is selected as the 2nd number rather than 5, else no 3rd number could be found to meet the prime conditions.
EXAMPLE
Table begins:
2
1,4
3,6,10
5,7,8,9
11,12,13,14,23
15,16,17,18,19,28
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Amarnath Murthy, Mar 23 2004
EXTENSIONS
Edited and extended by Ray Chandler, May 07 2008
STATUS
approved