id:A065928 - OEIS Search Results

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(x,y) = (a(n),a(n+1)) are the solutions of (t(x)+t(y))/(1+xy)) = t(2) = 3, where t(n) denotes the n-th triangular number t(n) = n(n+1)/2.

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2, 11, 63, 366, 2132, 12425, 72417, 422076, 2460038, 14338151, 83568867, 487075050, 2838881432, 16546213541, 96438399813, 562084185336, 3276066712202, 19094316087875, 111289829815047 (list; graph; listen)

	OFFSET	`0,1`
	LINKS	`J.-P. Ehrmann et al., Problem POLYA002, Integer pairs (x,y) for which (x^2+y^2)/(1+pxy) is an integer.`
	FORMULA	`a(n) = 2t(m)a(n-1)-a(n-2)-1, a(0) = m, a(1) = m^3+m^2-1 with m = 2.` `G.f.: (3x-2)/((1-6x+x^2)(x-1)).`
	CROSSREFS	`Sequence in context: A162274 A020078 A002629 this_sequence A114175 A080049 A126745` `Adjacent sequences: A065925 A065926 A065927 this_sequence A065929 A065930 A065931`
	KEYWORD	`easy,nonn`
	AUTHOR	`Floor van Lamoen (fvlamoen(AT)hotmail.com), Nov 29 2001`

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Last modified November 24 23:16 EST 2009. Contains 167481 sequences.

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