A137697 a(n) = x(n) * 2^((n mod 2 - 1)/2), with x(n)=Sum(x(k)*x(n-k-1):0<=k<n), x(0)=SQRT(2).

1, 2, 4, 20, 56, 336, 1056, 6864, 22880, 155584, 537472, 3762304, 13312768, 95091200, 342328320, 2481880320, 9051563520, 66378132480

Offset

0,2

Links

Table of n, a(n) for n=0..17.

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: A052004 A353342 A027741 * A192380 A009336 A274520

Adjacent sequences: A137694 A137695 A137696 * A137698 A137699 A137700

Keyword

nonn

Author

Reinhard Zumkeller, Feb 06 2008

Status

approved