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 A137697 a(n) = x(n) * 2^((n mod 2 - 1)/2), with x(n)=Sum(x(k)*x(n-k-1):0<=k
 1, 2, 4, 20, 56, 336, 1056, 6864, 22880, 155584, 537472, 3762304, 13312768, 95091200, 342328320, 2481880320, 9051563520, 66378132480 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS EXAMPLE x(1) = 2; x(2) = 5.6568... = a(2)*SQRT(2); x(3) = 20; x(4) = 79.1959... = a(4)*SQRT(2); x(5) = 336; x(6) = 1493.4095... = a(6)*SQRT(2). CROSSREFS Cf. A000108. Sequence in context: A294230 A052004 A027741 * A192380 A009336 A274520 Adjacent sequences:  A137694 A137695 A137696 * A137698 A137699 A137700 KEYWORD nonn AUTHOR Reinhard Zumkeller, Feb 06 2008 STATUS approved

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