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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 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.)