A133305 - OEIS

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A133305

(1/n)*Sum[i=0..n-1,C(n,i)*C(n,i-1)*4^i*5^(n-i)], a(0)=1 .

1, 5, 45, 505, 6345, 85405, 1204245 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,2`
	COMMENTS	`Fifth column of array A103209 .` `The Hankel transform of this sequence is 20^C(n+1,2). - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 28 2007`
	FORMULA	`G.f.: [1-z-(z^2-18z+1]^(1/2)]/(8z). a(n) = Sum_{k, 0<=k<=n}A088617(n,k)4^k . a(n) = Sum_{k, 0<=k<=n} A060693(n,k)4^(n-k). a(n) = Sum_{k, 0<=k<=n}C(n+k, 2k)4^kC(k), C(n) given by A000108 .` `a(0)=1, a(n)=a(n-1)+4Sum_{k, 0<=k<=n-1}a(k)*a(n-1-k) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 23 2007`
	CROSSREFS	`Cf. A000108 A060693 A103209 A103210 A103211.` `Sequence in context: A195188 A151831 A188267 * A189122 A062023 A169714` `Adjacent sequences: A133302 A133303 A133304 * A133306 A133307 A133308`
	KEYWORD	`nonn`
	AUTHOR	`Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 18 2007`

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Last modified February 14 18:09 EST 2012. Contains 205663 sequences.