id:A066786 - OEIS Search Results

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a(n) = least natural number k such that the distance between (n,EulerPhi(n)) and (n+k,EulerPhi(n+k)) is an integer (i.e. k^2+(EulerPhi(n+k)-EulerPhi(n))^2 is a square), if such k exists; = 0 otherwise.

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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; listen)

	OFFSET	`1,2`
	EXAMPLE	`12^2+(EulerPhi(2+12)-EulerPhi(2))^2 = 13^2, and k = 12 is the least natural number achieving this, so a(2) = 12.`
	CROSSREFS	`Adjacent sequences: A066783 A066784 A066785 this_sequence A066787 A066788 A066789` `Sequence in context: A022175 A015129 A010211 this_sequence A109015 A010210 A010212`
	KEYWORD	`nonn`
	AUTHOR	`Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 18 2002`

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Last modified October 7 14:39 EDT 2008. Contains 144666 sequences.

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