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A111554
Column 1 of triangle A111553.
2
1, 2, 10, 72, 632, 6352, 70912, 864192, 11371072, 160333952, 2409420032, 38428442112, 648333665792, 11538313372672, 216092576714752, 4249731095212032, 87591291183296512, 1888669450881032192
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
Cf. A111553.
Sequence in context: A271214 A366241 A321446 * A177384 A354288 A182525
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 07 2005
STATUS
approved