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 A066786 a(n) = least natural number k such that the distance between (n, phi(n)) and (n+k, phi(n+k)) is an integer (i.e., k^2 + (phi(n+k) - phi(n))^2 is a square), if such k exists; = 0 otherwise. 0
 1, 12, 1, 2, 3, 3, 2, 2, 5, 2, 3, 3, 3, 4, 1, 4, 15, 8, 8, 4, 3, 48, 23, 6, 5, 2, 8, 8, 5, 24, 8, 2, 11, 6, 4, 6, 20, 16, 6, 8, 7, 32, 6, 6, 6, 33, 8, 7, 8, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE 12^2 + (phi(2+12) - phi(2))^2 = 13^2 and k = 12 is the least natural number achieving this, so a(2) = 12. CROSSREFS Sequence in context: A172376 A289673 A010211 * A109015 A010210 A229193 Adjacent sequences:  A066783 A066784 A066785 * A066787 A066788 A066789 KEYWORD nonn AUTHOR Joseph L. Pe, Jan 18 2002 STATUS approved

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Last modified February 18 12:10 EST 2020. Contains 332018 sequences. (Running on oeis4.)