id:A076795 - OEIS Search Results

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Partial sums of (2n-1)!!.

+0
3

0, 1, 2, 5, 20, 125, 1070, 11465, 146600, 2173625, 36633050, 691362125, 14440672700, 330674815925, 8236528396550, 221694575073425, 6411977928702800, 198310761891213425, 6530970632654064050 (list; graph; listen)

	OFFSET	`0,3`
	FORMULA	`E.g.f.: exp(x)* Integral_{t=0, x} exp(-t)/sqrt(1-2t) dt.` `a(n)=a(n-1)(2n-2)-a(n-2)(2n-3) . a(n) ~ 1/sqrt(2)/n 2^n * (n/e)^n.`
	PROGRAM	`(PARI) a(n)=if(n<0, 0, sum(k=0, n-1, (2*k)!/k!/2^k))`
	CROSSREFS	`Cf. A001147.` `Sequence in context: A144503 A012321 A012519 this_sequence A130293 A156073 A006366` `Adjacent sequences: A076792 A076793 A076794 this_sequence A076796 A076797 A076798`
	KEYWORD	`nonn`
	AUTHOR	`Michael Somos, Nov 16 2002`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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