id:A063664 - OEIS Search Results

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Numbers whose reciprocal is the sum of two reciprocals of squares.

+0
4

2, 8, 18, 20, 32, 50, 72, 80, 90, 98, 128, 144, 162, 180, 200, 242, 272, 288, 320, 338, 360, 392, 450, 468, 500, 512, 576, 578, 648, 650, 720, 722, 800, 810, 882, 968, 980, 1058, 1088, 1152, 1250, 1280, 1296, 1332, 1352, 1440, 1458, 1568, 1620, 1682, 1800 (list; graph; listen)

	OFFSET	`0,1`
	COMMENT	`These are numbers which can be written either as b^2c^2(b^2+c^2)d^2 or if (b^2+c^2) is a square then as b^2c^2d^2, since 1/(b(b^2+c^2)d)^2+1/(c(b^2+c^2)d)^2 =1/(b^2c^2(b^2+c^2)d^2) and 1/(bsqrt(b^2+c^2)d)^2+1/(csqrt(b^2+c^2)d)^2 = 1/(b^2c^2d^2).`
	EXAMPLE	`98 is in the sequence since 1/98=1/10^2+1/70^2 (also 1/98=1/14^2+1/14^2).`
	CROSSREFS	`Either products of terms in A063663 and A000290, or squares of A008594. Cf. A001481, A000404, A063665, A063669.` `Sequence in context: A154349 A073601 A051248 this_sequence A094147 A117612 A171613` `Adjacent sequences: A063661 A063662 A063663 this_sequence A063665 A063666 A063667`
	KEYWORD	`nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Jul 28 2001`

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Last modified March 17 00:31 EDT 2010. Contains 173532 sequences.

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