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A117381 Expansion of 1/((1-4*x*c(x))(1-x^2*c(x))), c(x) the g.f. of A000108. 1
1, 4, 21, 109, 575, 3047, 16192, 86171, 458972, 2445825, 13037508, 69509558, 370634265, 1976421031, 10539858413, 56208784808, 299766435277, 1598704176149, 8526238418811, 45472594256564, 242517996824355 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Diagonal sums of number triangle A117380.

LINKS

Table of n, a(n) for n=0..20.

FORMULA

a(n)=sum{k=0..floor(n/2), [k<=n-k]*sum{j=0..n-k, (j/(n-k-j))*C(2n-k-j,n-k-j)[k<=j]*4^(j-k)}}

CROSSREFS

Sequence in context: A083425 A183367 A100237 * A010908 A136786 A026335

Adjacent sequences:  A117378 A117379 A117380 * A117382 A117383 A117384

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 10 2006

STATUS

approved

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Last modified December 11 16:06 EST 2017. Contains 295905 sequences.