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A179594 Y-coordinate of the first n*n non-coprime block above the line x=y in the first quadrant. 0
2, 20, 1308, 10199370, 131487690152 (list; graph; refs; listen; history; text; internal format)
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: A239642 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

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Last modified August 14 04:13 EDT 2020. Contains 336477 sequences. (Running on oeis4.)