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A166232 a(n) = A166231(n)/4^n. 5
1, 1, 3, 20, 272, 7424, 405504, 44302336, 9680453632, 4230542786560, 3697657604210688, 6463791365183504384, 22598414411798807576576, 158015104883301198495481856, 2209780998563745292895322636288 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n+1) is the Hankel transform of A068764.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..70

FORMULA

a(n) = 2^C(n,2)*Sum_{k=0..floor(n/2)} C(n,2k)*2^(-k).

a(n) = A166231(n)/4^n.

MATHEMATICA

Table[2^(Binomial[n, 2])*Sum[Binomial[n, 2 k]*2^(-k), {k, 0, Floor[n/2]}], {n, 0, 25}] (* G. C. Greubel, May 07 2016 *)

CROSSREFS

Cf. A068764, A166231.

Sequence in context: A197975 A210906 A193194 * A136551 A266812 A086229

Adjacent sequences:  A166229 A166230 A166231 * A166233 A166234 A166235

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Oct 09 2009

STATUS

approved

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Last modified February 21 15:58 EST 2018. Contains 299414 sequences. (Running on oeis4.)