OFFSET
0,2
COMMENTS
When aerated, gives Hankel transform of A138175.
LINKS
A. V. Razumov and Yu. G. Stroganov, On refined enumerations of some symmetry classes of alternating sign matrices, arXiv:math-ph/0312071, 2003.
FORMULA
sqrt(abs(a(n)))/2^n = A005156(n).
a(n) = (-1)^n*(Product_{k=1..n} (6*k-2)!*(2*k-1)!/((4*k-1)!*(4*k-2)!))^2.
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Mar 03 2008
STATUS
approved