A069140 - OEIS

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A069140

(4n-1)*4n*(4n+1).

0, 60, 504, 1716, 4080, 7980, 13800, 21924, 32736, 46620, 63960, 85140, 110544, 140556, 175560, 215940, 262080, 314364, 373176, 438900, 511920, 592620, 681384, 778596, 884640, 999900, 1124760, 1259604, 1404816, 1560780, 1727880, 1906500 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	COMMENTS	`Sum_i{i>0}1/a(i) =ln(2)*3/4-1/2 =0.019860... which is the ratio of the area of the deltoid envelope formed by area bisectors of a triangle to the area of the triangle.`
	LINKS	`H.G.Bottomley, Medians and area bisectors of a triangle` `S. Ramanujan, Notebook entry`
	FORMULA	`a(n) =64n^3-4n =A007531(4n) =A069072(2n-1)`
	EXAMPLE	`a(10)=394041=63960`
	CROSSREFS	`Cf. A097321.` `Sequence in context: A088943 A097387 A057096 * A184191 A101384 A081384` `Adjacent sequences: A069137 A069138 A069139 * A069141 A069142 A069143`
	KEYWORD	`easy,nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Apr 08 2002`

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Last modified February 15 21:56 EST 2012. Contains 205860 sequences.