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URL: https://oeis.org/A137697

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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<n), x(0)=SQRT(2).
1
1, 2, 4, 20, 56, 336, 1056, 6864, 22880, 155584, 537472, 3762304, 13312768, 95091200, 342328320, 2481880320, 9051563520, 66378132480
OFFSET
0,2
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: A353342 A027741 A385173 * A192380 A009336 A274520
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Feb 06 2008
STATUS
approved