id:A094572 - OEIS Search Results

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Number of pairs of integers x, y (of either sign) with x^2 - y^2 = n.

+0
1

2, 0, 4, 2, 4, 0, 4, 4, 6, 0, 4, 4, 4, 0, 8, 6, 4, 0, 4, 4, 8, 0, 4, 8, 6, 0, 8, 4, 4, 0, 4, 8, 8, 0, 8, 6, 4, 0, 8, 8, 4, 0, 4, 4, 12, 0, 4, 12, 6, 0, 8, 4, 4, 0, 8, 8, 8, 0, 4, 8, 4, 0, 12, 10, 8, 0, 4, 4, 8, 0, 4, 12, 4, 0, 12, 4, 8, 0, 4, 12, 10, 0, 4, 8, 8, 0, 8, 8, 4, 0, 8, 4, 8, 0, 8, 16, 4, 0, 12, 6 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`The old entry with this sequence number was a duplicate of A058071.`
	REFERENCES	`M. N. Huxley, Area, Lattice Points and Exponential Sums, Oxford, 1996; p. 236.`
	FORMULA	`a(n) = 2d(n) if n is odd, = 2d(n/4) if n == 0 mod 4, otherwise 0, where d() = A000005().`
	MAPLE	`with(numtheory); f:=proc(n) if n mod 2 = 1 then RETURN(2tau(n)); fi; if n mod 4 = 0 then RETURN(2tau(n/4)); fi; 0; end;`
	CROSSREFS	`Cf. A000005, A093061.` `Sequence in context: A155984 A028609 A107490 this_sequence A079534 A097042 A097945` `Adjacent sequences: A094569 A094570 A094571 this_sequence A094573 A094574 A094575`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), Nov 02 2008`

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Last modified December 2 11:54 EST 2009. Contains 167921 sequences.

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