OFFSET
1,1
COMMENTS
a(n) is the minimum y that satisfies x <= y and the GCD of (x,y),(x+1,y), ..., (x+n-1,y), (x,y+1),(x+1,y+1), ..., (x+n-1,y+1), ..., (x,y+n-1),(x+1,y+n-1), ..., (x+n-1,y+n-1) are all larger than 1.
REFERENCES
Stephen Wolfram, A New Kind of Science, Wolfram Media, 2002, p. 1093.
LINKS
The first 4 terms are found in Stephen Wolfram A New Kind of Science
The 5th term has been posted on bbs.emath.ac.cn
EXAMPLE
a(2)=20 because the GCDs of (14,20), (15,20), (14,21), (15,21) are all larger than 1, and there is no such array within x <= y < 20.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Yi Yang, Jul 20 2010
STATUS
approved