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A092467 a(n)=sum(i+j+k=n,(n+2k)!/i!/j!/(3*k)!) 0<=i,j,k<=n. 2
1, 3, 13, 63, 309, 1511, 7373, 35951, 175269, 854455, 4165565, 20307647, 99002389, 482649479, 2352978861, 11471077391, 55922991237, 272631840855, 1329115610269, 6479611111519, 31588945184245, 154000207833639 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

In general, sum{k=0..n, C(n+2k,3k)*r^k} has g.f. (1-r*x)^2/(1-(3r+1)*x+3r^2*x^2-r^3*x^3). - Paul Barry, Aug 23 2007

LINKS

Table of n, a(n) for n=0..21.

FORMULA

G.f.: (1-4x+4x^2)/(1-7x+12x^2-8x^3) (conjectured). - Ralf Stephan, Dec 02 2004

a(n)=sum{k=0..n, C(n+2k,3k)2^(n-k)}; - Paul Barry, Aug 23 2007

CROSSREFS

Cf. A007583.

Sequence in context: A186242 A276893 A284160 * A034478 A026715 A001850

Adjacent sequences:  A092464 A092465 A092466 * A092468 A092469 A092470

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Mar 25 2004

STATUS

approved

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Last modified February 19 16:28 EST 2018. Contains 299356 sequences. (Running on oeis4.)