A179594 Y-coordinate of the first n*n non-coprime block above the line x=y in the first quadrant.

2, 20, 1308, 10199370, 131487690152

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

Table of n, a(n) for n=1..5.

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

Sequence in context: A369679 A112359 A308231 * A196749 A263417 A053848

Adjacent sequences: A179591 A179592 A179593 * A179595 A179596 A179597

Keyword

nonn,hard,more

Author

Yi Yang, Jul 20 2010

Status

approved