OFFSET
0,2
COMMENTS
a(n) is the number of increasing strict binary trees with 2n-1 nodes that avoid 132. For more information about increasing strict binary trees with an associated permutation, see A245894. - Manda Riehl, Aug 07 2014
PROG
(PARI) {a(n)=if(n<0, 0, (matrix(n+2, n+2, m, j, if(m==j, 1, if(m==j+1, -m+1, -(m-j-1)*polcoeff(log(sum(i=0, m, (i+3)!/3!*x^i)), m-j-1))))^-1)[n+2, 2])}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 07 2005
STATUS
approved