A092266 - OEIS

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A092266

Expansion of (1+4x)/AGM(1+4x,1-4x) where AGM denotes the arithmetic-geometric mean.

1, 4, 4, 16, 36, 144, 400, 1600, 4900, 19600, 63504, 254016, 853776, 3415104, 11778624, 47114496, 165636900, 662547600, 2363904400, 9455617600, 34134779536, 136539118144, 497634306624, 1990537226496, 7312459672336 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	FORMULA	`G.f.: (1+4x)/AGM(1+4x, 1-4x) where AGM(x, y) is the arithmetic-geometric mean of Gauss and Legendre.` `a(n)=A063886(n)^2. a(2n)=A002894(n). a(2n+1)=4a(2n).`
	PROG	`(PARI) a(n)=((n==0)+2*binomial(n-1, (n-1)\2))^2`
	CROSSREFS	`Sequence in context: A158101 A038234 A099462 * A107382 A185567 A203536` `Adjacent sequences: A092263 A092264 A092265 * A092267 A092268 A092269`
	KEYWORD	`nonn`
	AUTHOR	`Michael Somos, Feb 16 2004`

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Last modified February 16 14:37 EST 2012. Contains 205930 sequences.