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A138269 a(n+1) is the Hankel transform of C(n)+C(n+2), where C(n)=A000108(n). 0
1, 3, 12, 53, 231, 1000, 4329, 18747, 81188, 351597, 1522639, 6594000, 28556241, 123666803, 535556412, 2319302053, 10044062391, 43497219000, 188370799289, 815766130347, 3532789487188, 15299239691997 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (5,-4,5,-1).

FORMULA

G.f.: (1-x)^2/(1-5x+4x^2-5x^3+x^4); a(n)=Re(P(2n,I)*CONJ(P(2n+1,I))) where I=sqrt(-1) and P(n,x)=sum{k=0..floor(n/2), C(n-k,k)x^k}.

CROSSREFS

Cf. A092886, A138268.

Sequence in context: A007198 A000256 A124202 * A228771 A151198 A151199

Adjacent sequences:  A138266 A138267 A138268 * A138270 A138271 A138272

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 10 2008

STATUS

approved

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Last modified August 28 05:09 EDT 2015. Contains 261118 sequences.